# GCN_circulars

GRB_name: GRB210318A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29672
SUBJECT: GRB 210318A: Swift-BAT refined analysis
DATE:    21/03/19 12:04:17 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm@nsf.gov>

T. Sakamoto (AGU), S. D. Barthelmy (GSFC), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), M. Stamatikos (OSU), E. Troja (NASA/GSFC, UMCP),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-60 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210318A (trigger #1037339)
(Troja, et al., GCN Circ. 29662).  The BAT ground-calculated position is
RA, Dec = 33.892, -37.755 deg which is 
  RA(J2000)  =  02h 15m 34.0s 
  Dec(J2000) = -37d 45' 17.7" 
with an uncertainty of 2.9 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 75%.

The mask-weighted light curves shows a single broad FRED-shaped peak with
some structure.  The emission starts at ~T10 sec, peaks at T+5 sec, and 
falls to background by T+50 sec.  T90 (15-350 keV) is 48.00 +- 22.63 sec 
(estimated error including systematics).

The time-averaged spectrum from T-12.37 to T+35.63 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.48 +- 0.33.  The fluence in the 15-150 keV band is 6.4 +- 1.3 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+11.13 sec in the 15-150 keV band
is 0.3 +- 0.3 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1037339/BA/


GRB_name: GRB200524A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29673
SUBJECT: GRB 200524A: Redshift from Gemini-North
DATE:    21/03/19 18:16:33 GMT
FROM:    Yuhan Yao at Caltech  <yyao@astro.caltech.edu>

Yuhan Yao (Caltech), Adam Miller (Northwestern), Anna Ho (UCB), Daniel Perley (LJMU)

We observed ZTF20abbiixp/AT2020kym (Ho et al., GCN #27799), the afterglow of the long-duration GRB 200524A (Pookalil et al., GCN #27809; Fana Dirirsa et al., GCN #27797; Gupta et al., GCN #27818; Svinkin et al., GCN #27867), with GMOS-N under our ToO program GN-2020A-Q-117 (PI: Miller). The observation, conducted in the Nod-and-Shuffle mode with a 1 arcsec slit, started at 2020-05-25 07:39:14.9 UT, corresponding to 26.6 hours after the Fermi-GBM trigger (Pookalil et al., GCN #27809). A power-law fit to the afterglow light curve (Ho et al., GCN #27799; Kumar et al., GCN #27800, #27804; Perley & Ho, GCN #27805) suggests that ZTF20abbiixp was at r=21.5 and g=21.8 at the time of Gemini observation.

We obtained 3 x 550 s spectroscopic exposures with the B600 grating and 3 x 550 s exposures with the R400 grating, providing coverage over the range 3620-9600 AA. No flux calibration was performed. The spectrum was reduced using the IRAF package for GMOS. A trace was detected redwards of 4900 AA. Bluewards of 4900 AA, the source was not significantly detected, probably because of the faintness of the object, the intrinsic red color of the afterglow (g-r ~ 0.3 mag) and low sensitivity at the blue end.

We clearly identified absorption lines of Mg II 2796 and Mg II 2803 at the redshift of z = 1.256 in the three individual exposures. Absorption from Mg I 2852 is marginally detected in the combined spectrum at consistent redshift. We therefore identify z=1.256 as the most probable redshift for the GRB, although in practice this is only a lower limit. The lack of a DLA or Lyman break places an upper limit of z < 3.


GRB_name: GRB201216C
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29674
SUBJECT: GRB 201216C: VIRT optical observations
DATE:    21/03/19 23:01:33 GMT
FROM:    Priyadarshini Gokuldass at U. of the Virgin Islands  <priyadass.94@gmail.com>

P. Gokuldass (UVI), D. Morris (UVI), N. Orange (OrangeWave Innovative
Science, LLC),
R. Strausbaugh (UVI), A. Cucchiara (UVI/College of Marin) report:

We observed the field of GRB201216C (V. Lipunov et al., GCN 29062) with the
0.5m Virgin Island Robotic Telescope (VIRT) at the University of the Virgin
Islands' Etelman Observatory on 12-16-2020 starting at 23:43:20.5 UT (T+36
mins).

We performed a series of exposures in R filter with a total exposure
of 2060 s. The weather conditions were very clear during the hours of
observation with an average arimass of 1.0.

We find no new source within the enhanced XRT position error circle
(S. Campana et al., 29064) and report the following 3-sigma upper limit:

T_mid       ||Exposure     ||Filter      ||Limit
T+ 1 hr      ||2060s           ||R            ||>20.65

The limit is estimated from comparison to nearby USNO B1 stars and is not
corrected for Galactic extinction. The VIRT is still in the commissioning
phase.

This work is supported by NASA-MUREP-MIRO grant NNX15AP95A, NSF EiR AST
Award 1901296, and NSF HBCU-UP AST Award 1831682. This message can be cited.


GRB_name: GRB210318B
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29675
SUBJECT: GRB 210318B: MITSuME Okayama optical upper limits
DATE:    21/03/20 02:11:32 GMT
FROM:    Ryohei Hosokawa at Tokyo Institute of Technology  <hosokawa@hp.phys.titech.ac.jp>

R. Hosokawa, K. L. Murata, R. Adachi, M. Niwano, F. Ogawa, N.Nakamura,
N. Ito, S. Ogata, H. Takamatsu, H. Hara, Y. Yatsu, and N.Kawai
(TokyoTech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 210318B (Troja et al. GCN Circular
#29663, Svinkin et al. GCN Circular #29664, Stamatikos et al. GCN
Circular #29666, Lipunov et al. GCN Circular #29667, Malacaria et al.
GCN Circular #29668) with the optical three color (g', Rc, and Ic) CCD
cameras attached to the MITSuME 50 cm telescope of Okayama
Astrophysical Observatory, Okayama, Japan. The observation with a
series of 60 sec exposures started at 2021-03-19 19:11:03 UT.(40.4
hours after Swift BAT trigger) We stacked the images with good
conditions. We did not find any new point sources within the Swift XRT
circle (Troja et al. GCN Circular #29663) in all three bands.
We obtained the 5-sigma limits of the stacked images as follows.

T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
40.4 19:50:32 2040 g'>14.3, Rc>14.2, Ic>13.4
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used the UCAC4 catalog for flux calibration.
The magnitudes are expressed in the AB system.
The images were processed in real-time through the MITSuME GPU
reduction pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1, Pages
4-24; https://github.com/MNiwano/Eclaire).


GRB_name: GRB210320A
Detection_method: MAXI Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29676
SUBJECT: GRB 210320A: MAXI/GSC detection
DATE:    21/03/21 02:24:37 GMT
FROM:    Hitoshi Negoro at Nihon U  <negoro@cygnus.phys.cst.nihon-u.ac.jp>

H. Negoro, M. Nakajima, M. Aoki, K. Kobayashi, R. Takagi, K. Asakura, K. Seino (Nihon U.), 
T. Mihara, T. Tamagawa, M. Matsuoka (RIKEN), 
T. Sakamoto, M. Serino, S. Sugita, H. Nishida, K. Komachi, A. Yoshida (AGU), 
Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, Y. Okamoto, S. Kitakoga (Chuo U.), 
M. Shidatsu (Ehime U.), N. Kawai, R. Adachi, M. Niwano, R. Hosokawa (Tokyo Tech), 
S. Nakahira, Y. Sugawara, S. Ueno, H. Tomida, M. Ishikawa, M. Tominaga, T. Nagatsuka (JAXA), 
Y. Ueda, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake, Y. Goto, R. Uematsu (Kyoto U.), 
H. Tsunemi (Osaka U.), M. Yamauchi, K. Kurogi, K. Miike (Miyazaki U.), 
T. Kawamuro (UDP/NAOJ), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU), M. Sugizaki (NAOC) 
report on behalf of the MAXI team:

The MAXI/GSC detected a bright uncatalogued soft X-ray transient source at 22:15 UT on 2021 March 20.
Assuming that the source flux was constant over the transit,
at 2-4 keV we obtain the source position at 
(R.A., Dec) = (4.731 deg, -47.476 deg) = (00 18 55, -47 28 34) (J2000)
with a 90% C.L. statistical error of 0.45 deg and an additional systematic uncertainty of 0.1 deg
 (90% containment radius), and, at 4-10 keV we obtained at 
(R.A., Dec) = (4.630 deg, -47.423 deg) = (00 18 31, -47 25 22) (J2000) 
with a statistical 90% C.L. elliptical error region 
with long and short radii of 0.64 deg and 0.61 deg, respectively. 
The roll angle of long axis from the north direction is 104.0 deg counterclockwise. 

The 2-4 keV and 4-10 keV X-ray fluxes averaged over the scan were 144 +- 28 mCrab 
and 59 +- 20 mCrab, respectively.

There was no significant excess flux in the previous transit at 20:42 UT 
and in the next transit at 01:21 UT on March 21 with an upper limit of 20 mCrab for each.
(Currently, there are no data at 23:47.)

There is no known bright X-ray source within the error regions,
and no significant short-term variations during the ~45 sec scan.
From the above nature, the source is likely a part of a long gamma-ray burst, 
but we tentatively name the source MAXI J0018-474.


GRB_name: GRB210321A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29677
SUBJECT: GRB 210321A: Swift detection of a burst
DATE:    21/03/21 07:22:33 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

S. Dichiara (NASA/GSFC/UMCP), C. Gronwall (PSU), H. A. Krimm (NSF),
K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 07:13:51 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210321A (trigger=1037828).  Swift did not immediately slew
due to an observing constraint. 
The BAT on-board calculated location is 
RA, Dec 87.874, +70.119 which is 
   RA(J2000) = 05h 51m 30s
   Dec(J2000) = +70d 07' 09"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of about 15 sec.  The peak count rate
was ~1300 counts/sec (15-350 keV), at ~1 sec after the trigger. 

Due to an observing constraint, Swift will not slew until T0+43.3
minutes. There will be no XRT or UVOT data until this time. 

Burst Advocate for this burst is S. Dichiara (dichiara AT umd.edu). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB210321A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29678
SUBJECT: GRB 210321A: Swift-XRT observations
DATE:    21/03/21 08:24:08 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

M. Perri (SSDC & INAF-OAR), P.A. Evans (U. Leicester), J.P. Osborne (U.
Leicester), D.N. Burrows (PSU), J.A. Kennea (PSU) and G. Cusumano
(INAF-IASF PA) report on behalf of the Swift-XRT team:

The XRT began observing the field of GRB 210321A at 07:59:21.6 UT,
2730.6 seconds after the BAT trigger. Using promptly downlinked data we
find an uncatalogued X-ray source located at RA, Dec 87.89627, 70.13042
which is equivalent to:
   RA(J2000)  = 05h 51m 35.10s
   Dec(J2000) = +70d 07' 49.5"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 49 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at https://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (1.13 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 4
(+3.35/-2.86) x 10^21 cm^-2 (90% confidence). 


GRB_name: GRB210321A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29679
SUBJECT: GRB 210321A: Swift/UVOT Detection
DATE:    21/03/21 13:35:49 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M.. H. Siegel (PSU) and S. Dichiara (NASA/GSFC/UMCP)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210321A
2735 s after the BAT trigger (Dichiara et al., GCN Circ. 29677).
A source consistent with the XRT position (Perri et al., GCN Circ. 29678)
is detected in the initial UVOT exposures.

Preliminary detections using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: 

Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white             2735         2837          100         18.76 +/- 0.11

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.116 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210321A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29680
SUBJECT: GRB 210321A: DDOTI Afterglow Confirmation
DATE:    21/03/21 14:54:00 GMT
FROM:    Nat Butler at Az State U  <natbutler@asu.edu>

Nat Butler (ASU), Alan M. Watson (UNAM), Rosa L. Becerra (UNAM), Simone
Dichiara (GSFC/UMD), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM),
OcÃ©lotl Lopez (UNAM), Diego Gonzalez (UNAM), Margarita Pereyra (UNAM),
Srihari Ravi (ASU), and Eleonora Troja (GSFC/UMD) report:

We observed the field of the Swift/BAT GRB 210321A (Dichiara et al., GCN
Circ.  29677) with the DDOTI wide-field imager at the Observatorio
AstronÃ³mico Nacional on Sierra San Pedro Martir (
http://ddoti.astroscu.unam.mx) starting at 2021-03-21 08:56 UTC (from 1.7
hours after the trigger).

We observed a region covering approximately 7 degrees in RA and 10 degrees
in declination (about 70 square degrees) centered on the XRT position
(Perri et al., GCN 29678) in the w filter.

Compared to the USNO-B1, Pan-STARRS DR1, and APASS DR10 catalogs, we detect
a bright source at 08:39:50.04 +60:12:18.9 (J2000) fading from about w =
18. This confirms the afterglow reported in UVOT observations by Siegel et
al. (GCN Circ.  29679).

We thank the staff of the Observatorio Astronomico Nacional in San Pedro
Martir.


GRB_name: GRB210321A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29681
SUBJECT: GRB 210321A: Enhanced Swift-XRT position
DATE:    21/03/21 15:54:59 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1720 s of XRT Photon Counting mode data and 5 UVOT
images for GRB 210321A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 87.89579, +70.13057 which is equivalent
to:

RA (J2000): 05h 51m 34.99s
Dec (J2000): +70d 07' 50.1"

with an uncertainty of 1.7 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB210321A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29683
SUBJECT: GRB 210321A: MASTER optical observation
DATE:    21/03/21 20:49:00 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, V.Kornilov, E.Gorbovskoy,N.Tiurina,P.Balanutsa,F.Balakin, 
V.Vladimirov, A.Kuznetsov,K.Zhirkov,D. Vlasenko, I.Gorbunov, D.Zimnukhov, 
V.Senik, A.Chasovnikov,A.Pozdnyakov,V.Topolev, D.Cheryasov(Lomonosov Moscow State University, SAI, Physics Department),
D. Buckley (South African Astronomical Observatory),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico FelixAguilar OAFA),
R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),
O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)

MASTER Global robotic net (MASTER-Net:http://observ.pereplet.ru Lipunov et al.,2010,Advances in Astronomy,2010,30L)
started Swift GRB 210321A (BAT:Dichiara et al. GCN 29677,Ttrig=07:13:51; 
XRT:Perri et al. GCN 29678,Beardmore et al. GCN29681;
UVOT: Siegel GCN29679), 
optical observations at MASTER-Tavrida at 2021-03-21 16:55:20UT, ~9.7h after trigger time,
with mlim=20.8m.
Swift optical counterpart (87.8947 +70.1305) isn't visible yet.

This message may be cited.


GRB_name: GRB210321A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29684
SUBJECT: GRB 210321A: NOT optical afterglow detection and redshift limit
DATE:    21/03/21 22:41:10 GMT
FROM:    Kasper Elm Heintz at Univ. of Iceland and DAWN/NBI  <keh14@hi.is>

Kasper E. Heintz (Univ. of Iceland, DAWN/NBI), Johan P. U. Fynbo (DAWN/NBI), and Tapio Pursimo (NOT), report on behalf of a larger collaboration:

We observed the field of the Swift/BAT-detected GRB 210321A (Dichiara et al., GCN #29677), using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Starting at 20:26:25.6 UTC on March 21, we obtained 3x300 sec exposures in the Sloan r-band. The observations were carried out under good conditions, with seeing around 0.8". We confirm the optical afterglow reported by Siegel et al. (GCN #29679), and measure r = 21.6 +/- 0.15 mag at 13.5 hr post-burst, calibrated against nearby field stars in the Pan-STARRS catalog. 

Following the imaging sequence, we obtained spectroscopy of the afterglow with ALFOSC using grism 4 (320 to 960 nm) and for 4x1200 sec total integration. A faint trace is detected but we do not identify any particular absorption or emission features to infer the redshift from. However, since the continuum is detected down to 380 nm, we put a limit on the redshift of z < 2.


GRB_name: GRB210321A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29685
SUBJECT: GRB 210321A: Redshift from OSIRIS/GTC
DATE:    21/03/21 22:57:51 GMT
FROM:    Antonio de Ugarte Postigo at IAA-CSIC  <deugarte@iaa.es>

A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), D.A. Kann, 
C. Thoene, M. Blazek, J.F. Agui Fernandez (all HETH/IAA-CSIC), 
S. Geier (GTC, IAC), A. Tejero (GTC) report:

We observed the afterglow of GRB 210321A (Dichiara et al. GCN 
29677; Perri et al. GCN 29678; Siegel et al. GCN 29679; Butler et 
al. GCN 29680; Heintz et al. GCN 29684) with OSIRIS at the 
10.4m GTC telescope at Roque de los Muchachos Observatory, 
in La Palma (Spain). The observation started at 20:28 UT (0.5517 
days after the burst), and consisted in 3x900s with grism R1000B, 
covering the spectral range from 3700 to 7800 AA.

The 30s acquisition image, with a seeing of 0.75â€œ, shows the 
afterglow at a magnitude of râ€™ = 21.39+/-0.03, using a nearby 
PanSTARRS field star as photometric reference.

The spectral continuum is well detected above 3900 AA, and 
shows very weak lines consistent with several features of FeII, MgII 
and MgI at a common redshift of z = 1.487, which we assume to be 
the likely redshift of the GRB. However, we note that strictly 
speaking this would be a lower limit, with the upper limit being z ~< 2, 
as already noted by the NOT spectroscopy (Heintz et al. GCN 29684).


GRB_name: GRB210321A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29686
SUBJECT: GRB 210321A: Swift-XRT refined Analysis
DATE:    21/03/21 23:16:40 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (U.
Leicester), M.G. Bernardini (INAF-OAB), E. Ambrosi  (INAF-IASFPA) , M.
Capalbi (INAF-IASFPA), D.N. Burrows (PSU), J. D. Gropp (PSU), J.A.
Kennea (PSU) and S. Dichiara report on behalf of the Swift-XRT team:

We have analysed 6.7 ks of XRT data for GRB 210321A (Dichiara et al.
GCN Circ. 29677), from 2.7 ks to 44.2 ks after the  BAT trigger. The
data are entirely in Photon Counting (PC) mode. The enhanced XRT
position for this burst was given by Beardmore et al. (GCN Circ.
29681).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.59 (+0.13, -0.11).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.99 (+0.20, -0.19). The
best-fitting absorption column is  2.3 (+0.8, -0.7) x 10^21 cm^-2, in
excess of the Galactic value of 1.1 x 10^21 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 3.6 x 10^-11 (5.1 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      2.3 (+0.8, -0.7) x 10^21 cm^-2
Galactic foreground: 1.1 x 10^21 cm^-2
Excess significance: 2.9 sigma
Photon index:      1.99 (+0.20, -0.19)

If the light curve continues to decay with a power-law decay index of
1.59, the count rate at T+24 hours will be 2.2 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.0 x
10^-14 (1.1 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01037828.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210321A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29687
SUBJECT: GRB 210321A:  Xinglong GWAC-F60A optical observation
DATE:    21/03/22 03:41:33 GMT
FROM:    Liping Xin at NAOC, SVOM  <xlp@nao.cas.cn>

L. P. Xin(NAOC),  C. Gao(GXU),  X. H. Han(NAOC), J. Y. Wei(NAOC), 
J. Wang(GXU), G. W. LI(NAOC),  L. H. Li(NAOC), C. Wu(NAOC), 
 X. G. Wang(GXU), E. W. Liang (GXU), Y. L. Qiu(NAOC), and J. S. Deng(NAOC) report: 

We began to observe GRB 210321A (Dichiara et al. GCN 
29677; Perri et al. GCN 29678; Siegel et al. GCN 29679; Butler et 
al. GCN 29680; Heintz et al. GCN 29684; Ugarte Postigo et al., GCN 29685)
with Xinglong GWAC-F60A telescope, China, at 11:30:49 (UT), 
21th. Mar. 2021, about 4.28 hours after the burst. 

A series of  R, I images were obtained.
The optical counterpart ( Siegel et al. GCN 29679; Butler et al. GCN 29680; 
Heintz et al. GCN 29684; Ugarte Postigo et al., GCN 29685)
was clearly detected in the stacked R-band image 
observed during 11:30:49 and 12:48:17 UT. 
The brightness was estimated to be 18.98 +/-0.13 mag at the mean
time of 4.88 hours after the burst, calibrated to USNO B1.0 R2 mag, 


This result is consistent with the previous report (Zhu et al., GCN 29530). 


GRB_name: GRB210321A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29689
SUBJECT: GRB 210321A: Mondy optical observations
DATE:    21/03/22 11:15:29 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

N. Pankov (HSE), A. Pozanenko (IKI), E. Klunko (ISTP), S. Belkin (IKI) 
report  on behalf of GRB IKI FuN:

We observed the field of GRB 210321A (Dichiara  et al., GCN 29677)  with 
AZT-33IK telescope of Sayan observatory (Mondy) starting on 2021-03-21 
(UT) 14:20:37. The optical afterglow (Siegel  et al., GCN 29679; Butler 
et al., GCN 29680;   Lipunov et al., GCN 29683; Heintz et al., GCN 
29684; de Ugarte Postigo et al., GCN 29685; Xin et al. GCN 29687) is 
clearly detected in a combined image. Preliminary photometry of the 
afterglow in the combined image is following

Date       UT start   t-T0       Filter Exp.   OT   Err.  UL(3sigma)
                       (mid, days)        (s)

2021-03-21 14:20:37   0.31199    R      45*60  20.1 0.14  20.5

The photometry is based on the nearby USNO-B1.0 stars
USNO-B1.0_id R2
1601-0068003 15.84
1600-0068970 16.18
1601-0068018 16.54
1601-0067995 16.23


GRB_name: GRB210321A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29691
SUBJECT: GRB 210321A: Swift-BAT refined analysis
DATE:    21/03/22 18:12:52 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm@nsf.gov>

T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC), S. Dichiara (NASA/GSFC/UMCP),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), (i.e. the Swift-BAT team):

Using the data set from T-240 to T+700 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210321A (trigger #1037828)
(Dichiara, et al., GCN Circ. 29677).  The BAT ground-calculated position is
RA, Dec = 87.887, 70.109 deg which is 
  RA(J2000)  =  05h 51m 32.8s 
  Dec(J2000) = +70d 06' 33.4" 
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 30%.

The mask-weighted light curve shows a single, fairly symmetrical peak from 
approximately T-8 to T+4 sec.  T90 (15-350 keV) is 8.21 +- 0.50 sec 
(estimated error including systematics).

The time-averaged spectrum from T-7.00 to T+1.84 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.15 +- 0.20.  The fluence in the 15-150 keV band is 6.7 +- 0.8 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-6.99 sec in the 15-150 keV band
is 1.7 +- 0.4 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1037828/BA/


GRB_name: GRB210321A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29692
SUBJECT: GRB 210321A: CrAO optical upper limit
DATE:    21/03/22 19:02:33 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

N. Pankov (HSE), S. Nazarov (CrAO), A. Pozanenko (IKI),  S. Belkin (IKI) 
report  on behalf of GRB IKI FuN:

We observed the field of GRB 210321A (Dichiara  et al., GCN 29677)  with 
AZT-8 telescope of CrAO observatory starting on 2021-03-21 (UT) 
19:04:11. The optical afterglow (Siegel  et al., GCN 29679; Butler et 
al., GCN 29680;   Lipunov et al., GCN 29683; Heintz et al., GCN 29684; 
de Ugarte Postigo et al., GCN 29685; Xin et al. GCN 29687; Pankov et 
al., GCN  29689) is not detected in a combined image. Preliminary 
photometry of the field  is following

Date       UT start   t-T0       Filter Exp.   OT   Err.  UL(3sigma)
                       (mid, days)        (s)

2021-03-21 19:04:11   0.51238    R      55*60  n/d  n/d   20.8

The photometry is based on the nearby USNO-B1.0 stars
USNO-B1.0_id R2
1601-0068003 15.84
1600-0068970 16.18
1601-0068018 16.54
1601-0067995 16.23


GRB_name: GRB210321A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29694
SUBJECT: GRB 210321A: DDOTI Position Correction
DATE:    21/03/22 19:42:51 GMT
FROM:    Nat Butler at Az State U  <natbutler@asu.edu>

The afterglow position quoted by Butler et al. (GCN 29680) was typed
incorrectly.  The correct position is 05:51:34.82, +70:07:50.4 (J2000).


GRB_name: GRB210318B
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29695
SUBJECT: GRB 210318B: Swift/UVOT Upper Limits
DATE:    21/03/23 03:30:27 GMT
FROM:    Sam LaPorte at PSU  <sjl5346@psu.edu>

 GRB 210318B: Swift/UVOT Upper Limits

M. H. Siegel (PSU) and E. Troja (NASA/GSFC, UMCP)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210318B
70 s after the BAT trigger (Troja et al., GCN Circ. 29663).
No optical afterglow consistent with the XRT position
(Troja et al. GCN Circular 29663)
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC            70          219          147         >20.0
u_FC               282          532          246         >20.1
white               70         1357          373         >20.9
v                  612         1406           97         >18.2
b                  538         1500           92         >19.1
u                  282         1479          324         >20.1
w1                 661         1455           97         >18.8
m2                1066         1430           58         >19.3
w2                 588         1382           97         >19.0

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 1.718 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210321A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29696
SUBJECT: Konus-Wind detection of GRB 210321A
DATE:    21/03/23 12:37:30 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

D. Frederiks, S. Golenetskii, A.Lysenko, D. Svinkin, A. Ridnaya,
A. Tsvetkova,  M. Ulanov, and T. Cline, report:

The long GRB 210321A (Swift-BAT trigger #1037828, T0(BAT)= 07:13:51.023 UT:
Dichiara, et al., GCN 29677; Ukwatta, et al., GCN 29691)
was detected by Konus-Wind (KW) in the waiting mode.

A Bayesian block analysis of the KW waiting mode data in the 20-400 keV band
reveals a ~10 sigma count rate increase over background in the interval
from ~T0(BAT)-6.430 s to ~T0(BAT)+2.402 s.

A fit to the KW 3-cannel waiting mode spectrum with by a power law with
an exponential cutoff (CPL) yields alpha~-2 and doesn't constrain Ep.
A fit with a simple power law (PL) gives a photon index of (2.19 Â± 0.17), chi^2 = 0.78/ 1 dof.
This result is consistent with the Swift-BAT refined analysis (GCN 29691).

In the 10 keV-10 MeV band, standard for the KW spectral analysis, the total burst fluence,
estimated from the PL model, is (1.6 Â± 0.3)x10^-6 erg/cm^2,
and the 2.944 s peak energy flux is (2.2 Â± 0.4)x10^-7 erg/cm^2.

Assuming the redshift z=1.487 (de Ugarte Postigo, et al., GCN 29685)
and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315,
and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the burst isotropic energy release E_iso to ~9.7x10^51 erg
and the isotropic luminosity L_iso to ~3.2x10^51 erg/s.

The KW light curve of this burst is available
at http://www.ioffe.ru/LEA/GRBs/GRB210321A/


GRB_name: GRB210321A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29697
SUBJECT: GRB 210321A: Swift/UVOT Detection
DATE:    21/03/23 14:17:59 GMT
FROM:    Sam LaPorte at PSU  <sjl5346@psu.edu>

 GRB 210321A: Swift/UVOT Detection

S. J. Laporte (PSU) and S. Dichiara (NASA/GSFC/UMCP)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210321A
2735 s after the BAT trigger (Dichiara et al., GCN Circ. 29677).
A source consistent with the XRT position
(Beardmore et al. GCN Circ. 29681)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  05:51:34.75 =  87.89479 (deg.)
    Dec (J2000) = +70:07:49.8  =  70.13051 (deg.)
with an estimated uncertainty of 0.49 arc sec. (radius, 90% confidence).

Preliminary detections and 3-sigma upper limits using the UVOT photometric
system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures
are:

Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white             2735         2885          147         18.69 +/- 0.09
v                 2892         4465          331         18.44 +/- 0.16
b                 3713         3913          197         18.64 +/- 0.11
u                 3507         3706          197         18.29 +/- 0.12
w1                3302         3502          197         18.48 +/- 0.17
m2                3097         3296          197        >18.9
w2                4124         4324          197        >19.8

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.118 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210323A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29699
SUBJECT: GRB 210323A: Swift detection of a short burst
DATE:    21/03/23 22:20:56 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

J.D. Gropp (PSU), F. E. Marshall (NASA/GSFC), M. J. Moss (GWU),
D. M. Palmer (LANL) and B. Sbarufatti (PSU) report on behalf of the
Neil Gehrels Swift Observatory Team:

At 22:02:18 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210323A (trigger=1038247).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 317.952, +25.378 which is 
   RA(J2000) = 21h 11m 49s
   Dec(J2000) = +25d 22' 40"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single spike
structure with a duration of about 1 sec.  The peak count rate
was ~10,000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 22:03:43.6 UT, 85.2 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source located at RA, Dec 317.94609, 25.36990 which
is equivalent to:
   RA(J2000)  = 21h 11m 47.06s
   Dec(J2000) = +25d 22' 11.6"
with an uncertainty of 3.5 arcseconds (radius, 90% containment). This
location is 34 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at https://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (1.17 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 5.9
(+3.84/-3.14) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 88 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.132. 

Burst Advocate for this burst is J.D. Gropp (jdg44 AT psu.edu). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB210323A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29700
SUBJECT: GRB 210323A: Nanshan/NEXT optical upper limit
DATE:    21/03/23 23:09:33 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

S.Y. Fu (NAOC), Z.P. Zhu (NAOC, HUST), X. Liu, D. Xu (NAOC), X. Gao 
(Urumqi No.1 Senior High School), J.Z. Liu (XAO) report:

We observed the field of GRB 210323A (Gropp et al., GCN 29699) using the 
NEXT-0.6m telescope located at Nanshan, Xinjiang, China. Observations 
automatically started at 22:03:49 UT on 2021-03-23 (i.e., 91 s after the 
BAT trigger), and 3x40 s, 4x60 s and 12x90 s frames were obtained in the 
Sloan r-filter.

No optical source is detected in our stacked image at the XRT position 
(Gropp et al., GCN 29699), down to a limiting magnitude of r~20.4, 
calibrated with nearby PanSTARRS stars.


GRB_name: GRB210323B
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29701
SUBJECT: GRB 210323B: Swift/BAT-GUANO detection and possible arcminute localization
DATE:    21/03/24 02:57:29 GMT
FROM:    Aaron Tohuvavohu at U Toronto  <aaron.tohu@gmail.com>

James DeLaunay (PSU), Aaron Tohuvavohu (U Toronto), Jamie Kennea (PSU) report:

Swift/BAT did not trigger on GRB 210323B (T0: 2021-03-23 12:03:33 UTC,
Fermi/GBM TRIGGER 638193818).

The Fermi/GBM notice, distributed in near real-time triggered the
Swift Mission Operations Center operated Gamma-ray Urgent Archiver for
Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).

Upon trigger by this notice, GUANO sent a command to the Swift Burst
Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from
[-50,+150] seconds around the time of the burst. All the requested
event mode data was delivered to the ground.

The burst is detected in BAT with a best fit duration of ~8 seconds.
With a maximum likelihood analysis (DeLaunay et al. 2021, in prep.) on
the event-mode data we detect a location for the burst with a square
root of the test statistic, sqrt(TS), of 11.77. The sqrt(TS) behaves
similarly to SNR.

This is a low significance detection and it could not be recovered
using the normal BAT imaging technique, so there is a chance that this
localization may be incorrect.

The BAT position is
RA, Dec = 259.664, +15.677 deg which is
  RA(J2000)  = 17h 18m 39.36s
  Dec(J2000) =  +15d 40' 37.20"
with an estimated uncertainty of 6 arcmin.

The partial coding was 10.6%

This position is consistent with the Fermi GBM localization.

XRT and UVOT follow-up has been requested. Results of follow-up
observations will be reported in future circulars.

GUANO is a fully autonomous, extremely low latency, spacecraft
commanding pipeline designed for targeted recovery of BAT event mode
data around the times of compelling astrophysical events to enable
more sensitive GRB searches.

A live reporting of Swift/BAT event data recovered by GUANO can be
found at: https://www.swift.psu.edu/guano/


GRB_name: GRB210323A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29702
SUBJECT: Swift GRB 210323A: Global MASTER-Net observations report 
DATE:    21/03/24 05:09:24 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-IAC robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Spain (IAC Teide Observatory) was pointed to the Swift GRB 210323A ( J.D. Gropp et al., GCN 29699) errorbox  20222 sec after notice time and 20288 sec after trigger time at 2021-03-24 03:40:27 UT, with upper limit up to  16.5 mag. The observations began at zenith distance = 84 deg. The sun  altitude  is -43.3 deg. 

The galactic latitude b = -16 deg., longitude l = 73 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1575256

We obtain a following upper limits.  

Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   20379 |          MASTER-IAC |   C |   180 | 16.5 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210323A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29703
SUBJECT: GRB 210323A: NOT optical afterglow candidate
DATE:    21/03/24 06:43:12 GMT
FROM:    Daniele B Malesani at DTU Space  <malesani@space.dtu.dk>

D. B. Malesani (DTU Space), A. de Ugarte Postigo (HETH/IAA-CSIC and 
DARK/NBI), Z. Zhu, D. Xu (NAO/CAS), D. A. Kann (HETH/IAA-CSIC), J. 
Martikainen (NOT and Univ. Helsinki) report on behalf of a larger 
collaboration:

We observed the field of the short GRB 210323A (Gropp et al., GCN 29699) 
using the Nordic Optical Telescope (NOT) equipped with the ALFOSC 
camera. Three observations of 10 min each were secured in the SDSS r 
filter, starting on 2021 Mar 24.229 UT (7.45 hr after the GRB). The 
field was observed at an airmass of ~2 and the seeing was 1.6".

No sources are detected within the currently available XRT error circle 
(3.5"; Gropp et al., GCN 29699). We note however the presence of an 
object about 2" S-E of the XRT circle, with coordinates (J2000):

RA = 21:11:47.33
DEC = +25:22:09.2

Its magnitude is r = 22.91 +- 0.09 AB, calibrated against nearby stars 
from Pan-STARRS. This object is not readily visible in the Pan-STARRS 
images, though its magnitude is close to the survey limit.

We consider this object as a viable afterglow candidate to GRB 210323A, 
but a confirmation is necessary to assess variability. Further 
observations are planned.


GRB_name: GRB210323A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29704
SUBJECT: GRB 210323A: Enhanced Swift-XRT position
DATE:    21/03/24 09:55:18 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1396 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 210323A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 317.94665, +25.36930 which is equivalent
to:

RA (J2000): 21h 11m 47.20s
Dec (J2000): +25d 22' 09.5"

with an uncertainty of 1.6 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB210323A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29705
SUBJECT: GRB 210323A: Swift-XRT refined Analysis
DATE:    21/03/24 10:23:44 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), E. Ambrosi 
(INAF-IASFPA) , M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR),
J. D. Gropp (PSU), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), J.P.
Osborne (U. Leicester) and J.D. Gropp report on behalf of the Swift-XRT
team:

We have analysed 6.8 ks of XRT data for GRB 210323A (Gropp et al. GCN
Circ. 29699), from 88 s to 34.2 ks after the  BAT trigger. The data
comprise 25 s in Windowed Timing (WT) mode with the remainder in Photon
Counting (PC) mode. The enhanced XRT position for this burst was given
by Evans et al. (GCN Circ. 29704).

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=1.69 (+0.17, -0.12). At T+719 s  the decay
flattens to an alpha of 0.46 (+0.09, -0.25) before breaking again at
T+12.2 ks to a final decay with index alpha=2.9 (+5.1, -0.6).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.70 (+0.20, -0.19). The
best-fitting absorption column is  2.7 (+1.0, -0.8) x 10^21 cm^-2, in
excess of the Galactic value of 1.2 x 10^21 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 4.4 x 10^-11 (5.6 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      2.7 (+1.0, -0.8) x 10^21 cm^-2
Galactic foreground: 1.2 x 10^21 cm^-2
Excess significance: 3.0 sigma
Photon index:      1.70 (+0.20, -0.19)

If the light curve continues to decay with a power-law decay index of
2.9, the count rate at T+24 hours will be 2.0 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.9 x
10^-15 (1.1 x 10^-14) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01038247.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210318A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29706
SUBJECT: GRB 210318A: Swift/UVOT Upper Limits
DATE:    21/03/24 11:05:42 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M. H. Siegel (PSU) and E. Troja (NASA/GSFC/UMCP)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210318A
127 s after the BAT trigger (Troja et al., GCN Circ. 29662).
No optical afterglow consistent with the XRT position
(Troja et al. GCN Circ. 29662)
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           127          277          147         >20.5
u_FC               285          535          246         >19.9
white              127         1188          353         >21.0
v                  614         1064           58         >18.6
b                  541         1163           58         >19.3
u                  285          535          246         >19.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.017 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210324A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29707
SUBJECT: GRB 210324A: Fermi GBM Final Real-time Localization
DATE:    21/03/24 11:24:43 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 11:14:28 UT on 24 Mar 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210324A (trigger 638277273.212466 / 210324468).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 148.5, Dec = 37.2 (J2000 degrees, equivalent to J2000 09h 54m, 37d 12'), with a statistical uncertainty of 3.1 degrees.

The angle from the Fermi LAT boresight is 76.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210324468/quicklook/glg_skymap_all_bn210324468.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210324468/quicklook/glg_healpix_all_bn210324468.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210324468/quicklook/glg_lc_medres34_bn210324468.gif


GRB_name: GRB210323A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29708
SUBJECT: GRB 210323A: Mondy optical observations, counterpart detection
DATE:    21/03/24 12:20:09 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

A. Pozanenko (IKI), N. Pankov (HSE), E. Klunko (ISTP), S. Belkin (IKI) 
report  on behalf of GRB IKI FuN:

We observed the field of short GRB 210323A (Gropp et al., GCN 29699) 
with AZT-33IK telescope of Sayan observatory (Mondy) starting on 
2021-03-23 (UT) 22:05:05, i.e. 167 s after GRB trigger. We obtained 10 
images in R-filter. In the first image we detect an object (S/N = 4.2) 
in coordinates of (J2000) 21:11:47.35, 25:22:09.4 with uncertainty of 
0.6" in each coordinate. The coordinates are in agreement with reported 
by NOT an afterglow candidate (Malesani  et al., GCN 29703)  and 
enhanced XRT position (Evans et al., GCN 29704). In the next two stacked 
images the object is barely detected (S/N =1.8), while in rest stacked 
images we do not detect the object.

Preliminary photometry of the object and the field in  stacked images is 
following

Date       UT start   t-T0       Filter Exp.   OT   Err.  UL(3sigma)
                       (mid, days)        (s)

2021-03-23 22:05:05   0.00229    R      1*60  18.4  0.25      18.9
2021-03-23 22:06:07   0.00333    R      2*60  19.2  S/N =1.8  19.0
2021-03-23 22:08:06   0.00403    R      5*60  n/d   n/d       18.9

The photometry is based on the nearby USNO-B1.0 star
USNO-B1.0_id R2
1153-0524625 14.44

The non-detection of the object in Nanshan/NEXT observations up to 
deeper limiting magnitude of r~20.4 (Fu et al., GCN 29700) might be due 
to searching of the afterglow in a stacked image but non in early single 
images.


GRB_name: GRB210323A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29709
SUBJECT: GRB 210323A: Fermi GBM detection
DATE:    21/03/24 13:30:47 GMT
FROM:    Rachel Hamburg at UAH  <rkh0007@uah.edu>

R. Hamburg (UAH) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 22:02:18.40 UT on 23 March 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210323A (trigger 638229743 / 210323918),
which was also detected by the Swift/BAT and Swift/XRT (Gropp et al. 2021,
GCN 29699). The GBM on-ground location is consistent with the Swift
position.

The angle from the Fermi LAT boresight at the GBM trigger time is 92
degrees.

The GBM light curve shows a single-peaked structure
with a duration (T90) of about 1 s (50-300 keV).
The time-averaged spectrum from T0-0.064 s to T0+0.192 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.97 +/- 0.05 and
the cutoff energy, parameterized as Epeak, is 2.1 +/- 0.4 MeV.
A Band function also fits the spectrum with Epeak = 2.1 +/- 0.5 MeV,
alpha = -0.97 +/- 0.05 and beta = -3.02 +/- 1.02.

The event fluence (10-1000 keV) in this time interval is
(1.2 +/- 0.1)E-06 erg/cm^2. The 64-ms peak photon flux measured
starting from T0+0.064 s in the 10-1000 keV band
is 21.3 +/- 1.5 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support
Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"


GRB_name: GRB210323A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29710
SUBJECT: GRB 210323A: Kitab optical upper limit
DATE:    21/03/24 15:05:43 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

N. Pankov (HSE), A. Pozanenko (IKI), A. Novichonok (Petrozavodsk State 
University, KIAM), A. Zhornichenko (KIAM), S. Belkin (IKI),  Sh. 
Ehgamberdiev (UBAI) report on behalf of GRB IKI FuN:

We observed the field of short GRB 210323A (Swift detection: Gropp et 
al., GCN 29699; GBM/Fermi detection: Hamburg et al., GCN 29709)
with  Kitab-ISON RC-36  telescope starting on 2021-03-23 (UT) 22:36:32. 
We obtained several images in Clear filter. We do not detect the 
afterglow candidate (Malesani et al., GCN 29703; Pozanenko et al., GCN 
29708) within enhanced Swift-XRT position (Evans et al., GCN 29704).
Preliminary photometry of the field is following

Date,      UT start, t-T0,   Exp.,  Filter,  OT,   Err., UL
                     (mid, days)

2021-03-23  22:36:32  0.02759 11*60 CR       n/d   n/d   16.6


The photometry is based on nearby USNO-B1.0 stars
USNO-B1.0_id R2
1153-0524361 15.3
1153-0524625 14.44
1153-0524441 15.36


GRB_name: GRB210323A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29711
SUBJECT: GRB 210323A: Classification and redshift estimation
DATE:    21/03/24 15:20:58 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

P. Minaev (IKI),  A. Pozanenko (IKI) report on behalf of GRB IKI FuN:

We analysed spectral data of GBM/Fermi of GRB 210323A (Hamburg et al., 
GCN 29709) which is initially reported in for GRB 210323A (Gropp et al., 
GCN 29699; Hamburg et al., GCN 29709) to classify the burst and estimate 
its redshift using EH-T90,i diagram [1,2]. The burst belongs to type I 
(short) population. We also estimate the lower limit on redshift of z = 
0.42.

See figure of EH-T90,i diagram for GRB 210323A at 
http://grb.rssi.ru/GRB210323A/GRB210323A_EH-T90.png

[1] â€” Minaev et al., MNRAS, 492, 1919 (2020)
[2] â€” Minaev et al., Astronomy Letters, 46, 573 (2020)


GRB_name: GRB210323A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29712
SUBJECT: GRB 210323A: Swift/UVOT Upper Limits
DATE:    21/03/24 15:26:43 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and J. D. Gropp (PSU) report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210323A 89 s after the BAT trigger 
(Gropp et al., GCN Circ. 29699). The optical afterglow detected by Malesani et al. (GCN Circ. 29703) 
and Pozanenko et al. (GCN Circ. 29708) and consistent with the XRT position (Evans et al. GCN Circ. 
29704), is not detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. 
Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC            89          239          147         >20.1
u_FC               302          552          246         >19.9
white               89         4948          569         >20.5
v                  632         1423           97         >17.7
b                  558         1522           97         >19.3
u                  302         1497          324         >19.3
w1                 681         1473           97         >18.5
m2                 828          848           19         >18.8
w2                 607         5034          136         >19.4

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of 
E(B-V) = 0.131 in the direction of the burst (Schlegel et al. 1998).


GRB_name: GRB210323A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29713
SUBJECT: Konus-Wind detection of GRB 210323A (short)
DATE:    21/03/24 16:09:47 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

D. Frederiks, S. Golenetskii, A.Lysenko, A. Ridnaia,
D. Svinkin, A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The short GRB 210323A (Swift-BAT detection:  Gropp et al., GCN 29699;
Fermi-GBM detection: Hamburg & Meegan, GCN 29709)
triggered Konus-Wind (KW) at T0=79334.600 s UT (22:02:14.600).

The burst light curve shows a single pulse with the total duration of ~0.45 s (20-1500 keV).
The emission is seen up to ~2 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210323_T79334/

As observed by Konus-Wind, the burst had
a fluence of 1.57(-0.25,+0.50)x10^-6 erg/cm^2 and
a 16-ms peak energy flux, measured from T0-0.016 s,
of 1.23(-0.20,+0.36)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

Since the brightest part of the burst emission was detected before the trigger,
the spectral analysis was performed using the KW 3-channel light curve data.

Modelling the time-integrated spectrum of the burst
(measured from T0-0.128 to T0+0.320 s)
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep),
yields alpha = -1.03(-0.17,+0.18) and Ep = 632(-167,+442) keV.

All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.


GRB_name: GRB210323B
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29714
SUBJECT: GRB 210323B: Swift ToO observations
DATE:    21/03/24 16:48:22 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a ToO observation of the Swift/BAT GRB 210323B. 
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021426

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Swift/BAT event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a 
GCN Circular after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210324B
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29715
SUBJECT: GRB 210324B: Fermi GBM Final Real-time Localization
DATE:    21/03/24 19:35:15 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 19:25:06 UT on 24 Mar 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210324B (trigger 638306711.486032 / 210324809).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 173.5, Dec = 6.5 (J2000 degrees, equivalent to J2000 11h 33m, 6d 30'), with a statistical uncertainty of 12.5 degrees.

The angle from the Fermi LAT boresight is 43.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210324809/quicklook/glg_skymap_all_bn210324809.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210324809/quicklook/glg_healpix_all_bn210324809.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210324809/quicklook/glg_lc_medres34_bn210324809.gif


GRB_name: GRB230312B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29716
SUBJECT: GRB 230312B: OSN Afterglow Observations
DATE:    21/03/24 19:45:39 GMT
FROM:    Alexander Kann at IAA-CSIC  <kann@iaa.es>

D. A. Kann (HETH/IAA-CSIC), M. Jelinek (ASU CAS Ondrejov), A. de Ugarte 
Postigo (HETH/IAA-CSIC, DARK/NBI), C. C. Thoene, M. Blazek, J. F. Agui 
Fernandez (all HETH/IAA-CSIC), A. Sota, and R. M. Eloy (both IAA-CSIC) 
report:

We observed the optical afterglow of GRB 210312B (INTEGRAL detection: 
Mereghetti et al., GCN #29650) with both the 1.5m T150 and the 0.9m T90 
telescopes of the Observatorio de Sierra Nevada (OSN),
Granada, Spain. We obtained 5 x 90 s exposures in B, V, Rc, and 6 x 90 s 
in Ic, followed by 21 x 180 s exposures in Rc with the T150 telescope, 
and 18 x 180 s in Rc with the T90 telescope in parallel, starting at 
2021-03-12 22:51:28.19 UT. The afterglow is detected in multiple 
combined images from T150, and in the complete combined T90 image. We 
furthermore obtained 10 x 500 s Rc images in the second night with the 
T150. The afterglow is detected in the combined image.

 From three stacked images observed from 0.09577 to 0.14106 days after 
the GRB, we detect a potential plateau phase, measuring Rc ~ 21.69 mag 
(AB mag, vs. a nearby Pan-STARRS star converted to Rc following the 
Lupton transformations, then transformed back to AB mag; errors range 
from 0.04 to 0.11 mag). Then at 1.0850 days, we find the afterglow has 
significantly decayed to Rc = 23.04 +/- 0.07 mag (AB).

Using photometry from our GTC observations (Kann et al., GCNs #29653, 
#29655) as well as earlier photometry from the Ondrejov D50, we find a 
broken power-law decay with a late slope of alpha ~ 2.2. The second-day 
OSN detection is in excess of the extrapolated decay, indicating that 
the host galaxy may contribute already, or that another rebrightening 
has taken place.


GRB_name: GRB210323A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29717
SUBJECT: Short GRB 210323A: GTC Observations
DATE:    21/03/24 19:49:17 GMT
FROM:    Alexander Kann at IAA-CSIC  <kann@iaa.es>

A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), D. A. Kann 
(HETH/IAA-CSIC), D. B. Malesani (DTU Space), N. R. Tanvir (Univ. 
Leicester), C. Thoene, M. Blazek, J. F. Agui Fernandez (all 
HETH/IAA-CSIC), and S. Geier (GTC, IAC) report:

We observed the afterglow (Malesani et al., GCN #29703, Pozanenko et 
al., GCN #29708) of the short/hard GRB 210323A (Swift detection: Gropp 
et al., GCN #29699, Fermi GBM detection: Hamburg & Meegan, GCN #29709; 
Konus-Wind detection: Frederiks et al., GCN #29713) with OSIRIS at the 
10.4m GTC telescope at Roque de los Muchachos Observatory, in La Palma 
(Spain). The observation started at 05:31 UT (0.3118 days after the 
burst), and consisted of 3 x 600s with grism R1000B, covering the 
spectral range from 3700 to 7800 AA. Observations were taken at high 
airmass, near dawn.

The 60 s acquisition image, with a seeing of 1".3, shows the afterglow 
at a magnitude of r' = 23.03 +/- 0.15 mag, using a nearby Pan-STARRS 
field star as photometric reference. This is in agreement with the NOT 
measurement.

Spectral continuum is faintly detected above 5000 AA, and shows no clear 
evidence for any absorption or emission lines. We therefore place a weak 
upper limit of z < 3.1 on the redshift of GRB 210323A. There may be 
evidence for a low-significance emission line at 5110 AA, which is 
slightly offset from the continuum trace in the 2D spectrum. It is found 
using multiple reductions and analyses. Interpreting this line as [OII], 
the corresponding redshift would be z = 0.37. However, we do not find 
any evidence for other emission lines, such as Hbeta and [OIII], at the 
corresponding redshift, placing its reality in doubt.

Further observations will be required to verify the reality of this 
feature and to attempt a redshift determination through host galaxy 
spectroscopy.


GRB_name: GRB210324C
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29718
SUBJECT: GRB 210324C: Fermi GBM Final Real-time Localization
DATE:    21/03/24 20:10:22 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 19:59:58 UT on 24 Mar 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210324C (trigger 638308803.321686 / 210324833).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 37.6, Dec = -46.0 (J2000 degrees, equivalent to J2000 02h 30m, -46d 00'), with a statistical uncertainty of 1.8 degrees.

The angle from the Fermi LAT boresight is 37.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210324833/quicklook/glg_skymap_all_bn210324833.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210324833/quicklook/glg_healpix_all_bn210324833.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210324833/quicklook/glg_lc_medres34_bn210324833.gif


GRB_name: GRB210324C
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29719
SUBJECT: GRB 210324C: BALROG localization (Fermi Trigger 638308803 / GRB 210324833)
DATE:    21/03/24 20:21:57 GMT
FROM:    Jochen Greiner at MPE,Garching  <jcg@mpe.mpg.de>

F. Kunzweiler, B. Biltzinger, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
638308803 at 19:59:58 on 24 March 2021 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).

The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 43.2+/-0.6 deg
Decl.(2000.0) = -48.1+/-0.5 deg
We estimate an additional systematic error of 2 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210324833/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210324833/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210324833/json

                        


GRB_name: GRB210323A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29720
SUBJECT: GRB 210323A: Gemini-North Optical Source Detection
DATE:    21/03/24 20:55:08 GMT
FROM:    Jillian Rastinejad at Northwestern Univ.  <jillianrastinejad2024@u.northwestern.edu>

J. Rastinejad, K. Paterson, W. Fong, C. D. Kilpatrick (Northwestern), T. Laskar (U. of Bath), A. Levan (Radboud U.), B. E. Cobb (GWU) report:

We observed the location of the Swift and Fermi short GRB 210323A (Gropp et al., GCN 29699, Hamburg et al., GCN 29709) with the Gemini Multi-object Spectrograph (GMOS) mounted on Gemini-North. We obtained 15x90-sec imaging in r-band at a mid-time of 2021 March 24.637 UT (0.72 days post-burst). Just to the East, outside of the updated XRT position (90% confidence; Evans et al., GCN 29704), we detect faint emission consistent with the putative optical afterglow (Malesani et al., GCN 29703, Pozanenko et al, GCN 29708, de Ugarte Postigo et al., GCN 29717). However, there is also a clear extension from this position to the North, which we propose to be a faint underlying host galaxy.

At present it is not possible to disentangle the contributions of faint afterglow and the underlying host. We measure a position for the source (or source complex) of RA = 21:11:47.34, Dec = +25:22:10.1 (J2000; 0.5'' uncertainty), ~0.7-0.9'' offset from the Mondy and NOT positions.

After calibrating our stacked image to isolated stars detected in the PS1 photometric catalog (Chambers et al., 2016), we perform aperture photometry of the entire extended source, and measure r = 24.6 +/- 0.2 AB mag (not corrected for Milky Way extinction). Compared to the NOT and GTC measurements Malesani et al., GCN 29703; de Ugarte Postigo et al., GCN 29717), this indicates fading of ~1.7 magnitudes over ~9.5 hours, indicating a rapid rate of decay of F~t^-1.86. This decline rate is likely contaminated by the host galaxy and the true decline rate is potentially steeper, consistent with the steep X-ray afterglow decline rate (Beardmore et al., GCN 29705).

Further observations are planned to assess any variability of the source. We thank Gemini staff Joan Font-Serra and Teo Mocnik for the rapid scheduling and execution of these observations.


GRB_name: GRB210323A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29721
SUBJECT: GRB 210323A: Swift-BAT refined analysis
DATE:    21/03/24 22:17:51 GMT
FROM:    Sibasish Laha at GSFC  <sibasish.laha@nasa.gov>

S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210323A (trigger #1038247)
(Gropp et al., GCN Circ. 29699).  The BAT ground-calculated position is
RA, Dec = 317.945, 25.352 deg which is
   RA(J2000)  =  21h 11m 46.7s
   Dec(J2000) = +25d 21' 08.7"
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 76%.

The BAT lightcurve showed complex structure with a duration less than 2 sec.
T90 (15-350 keV) is 1.12 +- 0.32 sec (estimated error including systematics).

The time-averaged spectrum from T-0.09 to T+1.26 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.46 +- 0.17.  The fluence in the 15-150 keV band is 2.4 +- 0.3 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T-0.10 sec in the 15-150 keV band
is 2.9 +- 0.3 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1038247/BA/


GRB_name: GRB210324B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29722
SUBJECT: Fermi GRB 210324B: Global MASTER-Net observations report 
DATE:    21/03/24 22:30:10 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-SAAO robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 210324B ( Fermi GBM team, GCN 29715) errorbox  525 sec after notice time and 535 sec after trigger time at 2021-03-24 19:34:01 UT, with upper limit up to  19.4 mag. The observations began at zenith distance = 39 deg. The sun  altitude  is -35.8 deg. 

MASTER-IAC robotic telescope  located in Spain (IAC Teide Observatory) started inspect of the Fermi GRB 210324B errorbox  1794 sec after notice time and 1804 sec after trigger time at 2021-03-24 19:55:11 UT, with upper limit up to  17.3 mag. Observations started at twilight.  The observations began at zenith distance = 71 deg. The sun  altitude  is -9.4 deg. 

MASTER-Tavrida robotic telescope  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 210324B errorbox  5260 sec after notice time and 5270 sec after trigger time at 2021-03-24 20:52:57 UT, with upper limit up to  15.5 mag. The observations began at zenith distance = 36 deg. The sun  altitude  is -42.7 deg. 

The galactic latitude b = 63 deg., longitude l = 259 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1575918

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

     565 | 2021-03-24 19:34:01 |         MASTER-SAAO | (10h 52m 40.19s , -01d 59m 36.4s) |   C |    60 | 19.2 |        
     725 | 2021-03-24 19:36:41 |         MASTER-SAAO | (11h 27m 56.31s , +05d 58m 47.1s) |   C |    60 | 19.3 |        
     804 | 2021-03-24 19:38:00 |         MASTER-SAAO | (11h 30m 57.79s , +08d 00m 40.5s) |   C |    60 | 18.7 |        
     884 | 2021-03-24 19:39:20 |         MASTER-SAAO | (11h 44m 14.69s , +06d 00m 20.8s) |   C |    60 | 18.3 |        
     963 | 2021-03-24 19:40:39 |         MASTER-SAAO | (11h 34m 47.03s , +10d 00m 50.8s) |   C |    60 | 18.8 |        
    1043 | 2021-03-24 19:41:59 |         MASTER-SAAO | (11h 41m 54.34s , +03d 58m 53.6s) |   C |    60 | 18.6 |        
    1123 | 2021-03-24 19:43:19 |         MASTER-SAAO | (11h 18m 32.07s , +10d 00m 48.9s) |   C |    60 | 19.2 |        
    1203 | 2021-03-24 19:44:39 |         MASTER-SAAO | (11h 40m 40.81s , +02d 00m 51.1s) |   C |    60 | 19.1 |        
    1283 | 2021-03-24 19:45:59 |         MASTER-SAAO | (11h 39m 31.24s , +12d 00m 52.3s) |   C |    60 | 18.1 |        
    1645 | 2021-03-24 19:52:01 |         MASTER-SAAO | (11h 01m 52.57s , -04d 01m 03.0s) |   C |    60 | 19.4 |        
    1835 | 2021-03-24 19:55:11 |          MASTER-IAC | (11h 31m 00.29s , -01d 51m 16.9s) |   C |    60 | 13.6 |        
    1835 | 2021-03-24 19:55:11 |          MASTER-IAC | (11h 22m 53.88s , -01d 46m 07.2s) |   C |    60 | 14.6 |        
    1884 | 2021-03-24 19:56:00 |         MASTER-SAAO | (10h 52m 39.43s , -01d 59m 07.9s) |   C |    60 | 19.2 |        
    1927 | 2021-03-24 19:56:43 |          MASTER-IAC | (11h 43m 11.33s , +14d 08m 01.9s) |   C |    60 | 15.2 |        
    1927 | 2021-03-24 19:56:43 |          MASTER-IAC | (11h 51m 33.96s , +14d 02m 55.4s) |   C |    60 | 14.5 |        
    1964 | 2021-03-24 19:57:20 |         MASTER-SAAO | (11h 00m 35.18s , -02d 00m 00.9s) |   C |    60 | 19.3 |        
    2209 | 2021-03-24 20:01:25 |         MASTER-SAAO | (11h 27m 55.48s , +05d 58m 59.6s) |   C |    60 | 19.4 |        
    2289 | 2021-03-24 20:02:45 |         MASTER-SAAO | (11h 36m 04.97s , +05d 59m 18.2s) |   C |    60 | 19.1 |        
    2548 | 2021-03-24 20:07:04 |         MASTER-SAAO | (11h 30m 52.80s , +08d 01m 07.1s) |   C |    60 | 19.2 |        
    2627 | 2021-03-24 20:08:23 |         MASTER-SAAO | (11h 39m 04.20s , +08d 00m 06.5s) |   C |    60 | 19.2 |        
    2682 | 2021-03-24 20:09:18 |          MASTER-IAC | (11h 47m 03.23s , -01d 53m 05.0s) |   C |    60 | 15.0 |        
    2682 | 2021-03-24 20:09:18 |          MASTER-IAC | (11h 38m 58.92s , -01d 47m 46.0s) |   C |    60 | 15.3 |        
    2707 | 2021-03-24 20:09:43 |         MASTER-SAAO | (11h 44m 00.61s , +05d 59m 07.1s) |   C |    60 | 19.1 |        
    2762 | 2021-03-24 20:10:38 |          MASTER-IAC | (11h 31m 04.71s , -01d 51m 41.8s) |   C |    60 | 15.5 |        
    2762 | 2021-03-24 20:10:38 |          MASTER-IAC | (11h 23m 00.29s , -01d 46m 23.6s) |   C |    60 | 15.8 |        
    2787 | 2021-03-24 20:11:03 |         MASTER-SAAO | (11h 52m 10.89s , +05d 59m 19.6s) |   C |    60 | 19.4 |        
    2842 | 2021-03-24 20:11:58 |          MASTER-IAC | (11h 51m 46.35s , +14d 07m 37.1s) |   C |    60 | 16.2 |        
    2842 | 2021-03-24 20:11:58 |          MASTER-IAC | (11h 43m 26.68s , +14d 13m 01.4s) |   C |    60 | 16.2 |        
    2867 | 2021-03-24 20:12:23 |         MASTER-SAAO | (11h 34m 47.24s , +10d 01m 07.5s) |   C |    60 | 19.2 |        
    2935 | 2021-03-24 20:13:31 |          MASTER-IAC | (11h 54m 11.42s , +00d 09m 29.0s) |   C |    60 | 15.4 |        
    2935 | 2021-03-24 20:13:31 |          MASTER-IAC | (12h 02m 16.97s , +00d 04m 02.2s) |   C |    60 | 14.6 |        
    2947 | 2021-03-24 20:13:43 |         MASTER-SAAO | (11h 42m 54.57s , +09d 59m 17.5s) |   C |    60 | 19.1 |        
    3026 | 2021-03-24 20:15:02 |         MASTER-SAAO | (11h 41m 59.41s , +04d 01m 00.7s) |   C |    60 | 19.2 |        
    3033 | 2021-03-24 20:15:09 |          MASTER-IAC | (11h 32m 22.11s , -03d 52m 14.7s) |   C |    60 | 15.5 |        
    3033 | 2021-03-24 20:15:09 |          MASTER-IAC | (11h 24m 16.52s , -03d 47m 01.3s) |   C |    60 | 15.7 |        
    3106 | 2021-03-24 20:16:22 |         MASTER-SAAO | (11h 49m 53.79s , +04d 00m 09.6s) |   C |    60 | 19.3 |        
    3113 | 2021-03-24 20:16:29 |          MASTER-IAC | (12h 03m 01.27s , -01d 53m 17.9s) |   C |    60 | 14.2 |        
    3113 | 2021-03-24 20:16:29 |          MASTER-IAC | (11h 54m 56.48s , -01d 47m 58.2s) |   C |    60 | 15.6 |        
    3186 | 2021-03-24 20:17:42 |         MASTER-SAAO | (11h 18m 29.74s , +10d 01m 14.9s) |   C |    60 | 19.3 |        
    3201 | 2021-03-24 20:17:56 |          MASTER-IAC | (11h 16m 21.10s , -03d 53m 09.2s) |   C |    60 | 16.3 |        
    3201 | 2021-03-24 20:17:56 |          MASTER-IAC | (11h 08m 15.23s , -03d 47m 56.1s) |   C |    60 | 16.4 |        
    3265 | 2021-03-24 20:19:01 |         MASTER-SAAO | (11h 26m 43.21s , +10d 00m 14.2s) |   C |    60 | 19.2 |        
    3280 | 2021-03-24 20:19:16 |          MASTER-IAC | (11h 58m 31.98s , +16d 08m 38.7s) |   C |    60 | 16.4 |        
    3280 | 2021-03-24 20:19:16 |          MASTER-IAC | (11h 50m 06.97s , +16d 13m 59.9s) |   C |    60 | 16.1 |        
    3345 | 2021-03-24 20:20:21 |         MASTER-SAAO | (11h 40m 35.20s , +01d 59m 13.9s) |   C |    60 | 19.2 |        
    3360 | 2021-03-24 20:20:36 |          MASTER-IAC | (12h 04m 24.29s , -03d 53m 05.8s) |   C |    60 | 14.2 |        
    3360 | 2021-03-24 20:20:36 |          MASTER-IAC | (11h 56m 18.44s , -03d 47m 45.0s) |   C |    60 | 15.5 |        
    3425 | 2021-03-24 20:21:41 |         MASTER-SAAO | (11h 48m 42.90s , +01d 59m 32.1s) |   C |    60 | 19.2 |        
    3504 | 2021-03-24 20:23:00 |         MASTER-SAAO | (11h 39m 31.85s , +12d 00m 48.7s) |   C |    60 | 19.1 |        
    3584 | 2021-03-24 20:24:20 |         MASTER-SAAO | (11h 47m 42.06s , +11d 59m 12.3s) |   C |    60 | 19.1 |        
    3659 | 2021-03-24 20:25:35 |          MASTER-IAC | (11h 46m 59.68s , -01d 52m 20.6s) |   C |    60 | 15.7 |        
    3659 | 2021-03-24 20:25:35 |          MASTER-IAC | (11h 38m 54.65s , -01d 47m 03.0s) |   C |    60 | 15.8 |        
    3739 | 2021-03-24 20:26:55 |          MASTER-IAC | (11h 31m 00.21s , -01d 51m 24.4s) |   C |    60 | 16.3 |        
    3739 | 2021-03-24 20:26:55 |          MASTER-IAC | (11h 22m 54.93s , -01d 46m 06.3s) |   C |    60 | 16.2 |        
    3743 | 2021-03-24 20:26:59 |         MASTER-SAAO | (11h 01m 53.12s , -03d 59m 35.4s) |   C |    60 | 19.0 |        
    3819 | 2021-03-24 20:28:15 |          MASTER-IAC | (11h 51m 53.44s , +14d 07m 37.7s) |   C |    60 | 16.6 |        
    3819 | 2021-03-24 20:28:15 |          MASTER-IAC | (11h 43m 32.87s , +14d 13m 01.5s) |   C |    60 | 16.7 |        
    3898 | 2021-03-24 20:29:34 |          MASTER-IAC | (11h 54m 29.64s , +00d 12m 00.1s) |   C |    60 | 16.0 |        
    3898 | 2021-03-24 20:29:34 |          MASTER-IAC | (12h 02m 34.62s , +00d 06m 38.3s) |   C |    60 | 15.6 |        
    3981 | 2021-03-24 20:30:57 |          MASTER-IAC | (11h 32m 23.14s , -03d 53m 07.0s) |   C |    60 | 16.3 |        
    3981 | 2021-03-24 20:30:57 |          MASTER-IAC | (11h 24m 16.91s , -03d 47m 48.6s) |   C |    60 | 16.2 |        
    3982 | 2021-03-24 20:30:58 |         MASTER-SAAO | (10h 52m 47.22s , -02d 00m 33.5s) |   C |    60 | 18.8 |        
    4061 | 2021-03-24 20:32:17 |          MASTER-IAC | (12h 03m 04.63s , -01d 51m 39.1s) |   C |    60 | 15.6 |        
    4061 | 2021-03-24 20:32:17 |          MASTER-IAC | (11h 54m 59.47s , -01d 46m 17.1s) |   C |    60 | 15.9 |        
    4062 | 2021-03-24 20:32:18 |         MASTER-SAAO | (11h 00m 50.00s , -02d 00m 15.6s) |   C |    60 | 19.0 |        
    4140 | 2021-03-24 20:33:36 |          MASTER-IAC | (11h 16m 17.56s , -03d 53m 01.1s) |   C |    60 | 16.6 |        
    4140 | 2021-03-24 20:33:36 |          MASTER-IAC | (11h 08m 11.22s , -03d 47m 43.8s) |   C |    60 | 16.6 |        
    4220 | 2021-03-24 20:34:56 |          MASTER-IAC | (11h 58m 36.00s , +16d 08m 17.4s) |   C |    60 | 16.7 |        
    4220 | 2021-03-24 20:34:56 |          MASTER-IAC | (11h 50m 10.51s , +16d 13m 42.5s) |   C |    60 | 16.5 |        
    4300 | 2021-03-24 20:36:16 |          MASTER-IAC | (12h 04m 22.11s , -03d 52m 23.2s) |   C |    60 | 15.9 |        
    4300 | 2021-03-24 20:36:16 |          MASTER-IAC | (11h 56m 16.04s , -03d 47m 01.5s) |   C |    60 | 16.0 |        
    4380 | 2021-03-24 20:37:36 |          MASTER-IAC | (10h 58m 59.33s , -01d 51m 36.6s) |   C |    60 | 16.9 |        
    4380 | 2021-03-24 20:37:36 |          MASTER-IAC | (10h 50m 53.48s , -01d 46m 20.7s) |   C |    60 | 16.6 |        
    4460 | 2021-03-24 20:38:56 |          MASTER-IAC | (11h 32m 21.51s , +04d 07m 35.0s) |   C |    60 | 16.6 |        
    4460 | 2021-03-24 20:38:56 |          MASTER-IAC | (11h 24m 14.72s , +04d 12m 54.5s) |   C |    60 | 17.0 |        
    4540 | 2021-03-24 20:40:16 |          MASTER-IAC | (11h 00m 13.15s , -03d 53m 36.3s) |   C |    60 | 17.0 |        
    4620 | 2021-03-24 20:41:36 |          MASTER-IAC | (11h 47m 06.09s , -01d 52m 56.2s) |   C |    60 | 16.1 |        
    4620 | 2021-03-24 20:41:36 |          MASTER-IAC | (11h 39m 00.51s , -01d 47m 36.2s) |   C |    60 | 16.2 |        
    4700 | 2021-03-24 20:42:56 |          MASTER-IAC | (11h 48m 22.11s , +04d 08m 19.7s) |   C |    60 | 16.4 |        
    4700 | 2021-03-24 20:42:56 |          MASTER-IAC | (11h 40m 15.30s , +04d 13m 40.6s) |   C |    60 | 16.4 |        
    4780 | 2021-03-24 20:44:15 |          MASTER-IAC | (11h 18m 21.52s , +06d 06m 57.3s) |   C |    60 | 17.1 |        
    4780 | 2021-03-24 20:44:15 |          MASTER-IAC | (11h 10m 12.82s , +06d 12m 15.8s) |   C |    60 | 16.7 |        
    4860 | 2021-03-24 20:45:36 |          MASTER-IAC | (12h 02m 40.48s , +00d 08m 24.6s) |   C |    60 | 16.3 |        
    4860 | 2021-03-24 20:45:36 |          MASTER-IAC | (11h 54m 35.16s , +00d 13m 45.5s) |   C |    60 | 16.2 |        
    4940 | 2021-03-24 20:46:56 |          MASTER-IAC | (11h 32m 17.35s , -03d 52m 23.9s) |   C |    60 | 16.4 |        
    4940 | 2021-03-24 20:46:56 |          MASTER-IAC | (11h 24m 10.73s , -03d 47m 06.2s) |   C |    60 | 16.4 |        
    5020 | 2021-03-24 20:48:16 |          MASTER-IAC | (12h 03m 02.56s , -01d 51m 22.2s) |   C |    60 | 16.1 |        
    5020 | 2021-03-24 20:48:16 |          MASTER-IAC | (11h 54m 56.99s , -01d 46m 01.2s) |   C |    60 | 16.2 |        
    5100 | 2021-03-24 20:49:36 |          MASTER-IAC | (11h 16m 20.74s , -03d 52m 28.7s) |   C |    60 | 16.5 |        
    5100 | 2021-03-24 20:49:36 |          MASTER-IAC | (11h 08m 13.95s , -03d 47m 12.3s) |   C |    60 | 16.6 |        
    5180 | 2021-03-24 20:50:56 |          MASTER-IAC | (11h 31m 01.78s , +02d 06m 35.4s) |   C |    60 | 16.7 |        
    5180 | 2021-03-24 20:50:56 |          MASTER-IAC | (11h 22m 55.65s , +02d 11m 54.2s) |   C |    60 | 16.7 |        
    5260 | 2021-03-24 20:52:16 |          MASTER-IAC | (11h 58m 34.84s , +16d 07m 03.0s) |   C |    60 | 16.8 |        
    5260 | 2021-03-24 20:52:16 |          MASTER-IAC | (11h 50m 08.91s , +16d 12m 26.9s) |   C |    60 | 16.6 |        
    5301 | 2021-03-24 20:52:57 |      MASTER-Tavrida | (11h 15m 19.39s , +08d 07m 00.4s) |   C |    60 | 15.5 |        
    5340 | 2021-03-24 20:53:36 |          MASTER-IAC | (12h 04m 24.32s , -03d 51m 46.5s) |   C |    60 | 16.3 |        
    5340 | 2021-03-24 20:53:36 |          MASTER-IAC | (11h 56m 17.85s , -03d 46m 26.8s) |   C |    60 | 16.3 |        
    5420 | 2021-03-24 20:54:56 |          MASTER-IAC | (10h 59m 03.12s , -01d 53m 20.5s) |   C |    60 | 16.9 |        
    5420 | 2021-03-24 20:54:56 |          MASTER-IAC | (10h 50m 56.86s , -01d 48m 05.4s) |   C |    60 | 16.7 |        
    5500 | 2021-03-24 20:56:16 |          MASTER-IAC | (11h 47m 07.30s , +02d 08m 14.3s) |   C |    60 | 16.6 |        
    5500 | 2021-03-24 20:56:16 |          MASTER-IAC | (11h 39m 01.21s , +02d 13m 33.9s) |   C |    60 | 16.3 |        
    5579 | 2021-03-24 20:57:35 |          MASTER-IAC | (11h 53m 33.35s , +08d 07m 38.7s) |   C |    60 | 16.8 |        
    5579 | 2021-03-24 20:57:35 |          MASTER-IAC | (11h 45m 22.48s , +08d 12m 59.8s) |   C |    60 | 16.8 |        
    5659 | 2021-03-24 20:58:55 |          MASTER-IAC | (11h 32m 16.32s , +04d 08m 36.5s) |   C |    60 | 16.8 |        
    5659 | 2021-03-24 20:58:55 |          MASTER-IAC | (11h 24m 08.97s , +04d 13m 55.4s) |   C |    60 | 17.0 |        
    5739 | 2021-03-24 21:00:15 |          MASTER-IAC | (11h 00m 19.84s , -03d 52m 36.3s) |   C |    60 | 16.9 |        
    5826 | 2021-03-24 21:01:42 |          MASTER-IAC | (11h 48m 19.78s , +04d 06m 39.0s) |   C |    60 | 16.7 |        
    5826 | 2021-03-24 21:01:42 |          MASTER-IAC | (11h 40m 12.56s , +04d 11m 58.5s) |   C |    60 | 16.6 |        
    5906 | 2021-03-24 21:03:02 |          MASTER-IAC | (11h 18m 23.44s , +06d 06m 58.1s) |   C |    60 | 17.2 |        
    5906 | 2021-03-24 21:03:02 |          MASTER-IAC | (11h 10m 14.27s , +06d 12m 15.7s) |   C |    60 | 16.9 |        
    5985 | 2021-03-24 21:04:21 |          MASTER-IAC | (11h 16m 17.20s , +04d 08m 19.5s) |   C |    60 | 17.2 |        
    5985 | 2021-03-24 21:04:21 |          MASTER-IAC | (11h 08m 09.58s , +04d 13m 36.5s) |   C |    60 | 16.9 |        
    6075 | 2021-03-24 21:05:51 |          MASTER-IAC | (11h 30m 38.78s , +00d 06m 50.7s) |   C |    60 | 16.6 |        
    6075 | 2021-03-24 21:05:51 |          MASTER-IAC | (11h 22m 32.66s , +00d 12m 07.6s) |   C |    60 | 16.8 |        
    6155 | 2021-03-24 21:07:11 |          MASTER-IAC | (11h 31m 06.20s , +02d 08m 25.1s) |   C |    60 | 16.9 |        
    6155 | 2021-03-24 21:07:11 |          MASTER-IAC | (11h 22m 59.66s , +02d 13m 42.6s) |   C |    60 | 17.0 |        
    6258 | 2021-03-24 21:08:54 |          MASTER-IAC | (11h 29m 41.70s , +12d 07m 34.6s) |   C |    60 | 17.0 |        
    6258 | 2021-03-24 21:08:54 |          MASTER-IAC | (11h 21m 23.88s , +12d 12m 54.2s) |   C |    60 | 16.9 |        
    6273 | 2021-03-24 21:09:09 |         MASTER-SAAO | (11h 28m 15.10s , +06d 00m 47.2s) |   C |    60 | 18.6 |        
    6338 | 2021-03-24 21:10:14 |          MASTER-IAC | (10h 58m 59.25s , -01d 51m 37.2s) |   C |    60 | 17.0 |        
    6338 | 2021-03-24 21:10:14 |          MASTER-IAC | (10h 50m 52.53s , -01d 46m 23.6s) |   C |    60 | 16.7 |        
    6418 | 2021-03-24 21:11:34 |          MASTER-IAC | (11h 47m 06.70s , +02d 07m 39.9s) |   C |    60 | 16.7 |        
    6418 | 2021-03-24 21:11:34 |          MASTER-IAC | (11h 39m 00.18s , +02d 12m 57.8s) |   C |    60 | 16.5 |        
    6498 | 2021-03-24 21:12:54 |          MASTER-IAC | (11h 53m 32.73s , +08d 06m 39.5s) |   C |    60 | 17.0 |        
    6498 | 2021-03-24 21:12:54 |          MASTER-IAC | (11h 45m 21.45s , +08d 11m 59.6s) |   C |    60 | 17.0 |        
    6530 | 2021-03-24 21:13:26 |         MASTER-SAAO | (11h 36m 12.72s , +06d 01m 18.7s) |   C |    60 | 18.5 |        
    6578 | 2021-03-24 21:14:14 |          MASTER-IAC | (12h 04m 26.90s , +04d 07m 00.2s) |   C |    60 | 16.8 |        
    6578 | 2021-03-24 21:14:14 |          MASTER-IAC | (11h 56m 19.50s , +04d 12m 20.2s) |   C |    60 | 16.8 |        
    6610 | 2021-03-24 21:14:46 |         MASTER-SAAO | (11h 31m 12.97s , +08d 00m 50.8s) |   C |    60 | 18.6 |        
    6658 | 2021-03-24 21:15:34 |          MASTER-IAC | (11h 57m 33.99s , +10d 08m 21.0s) |   C |    60 | 16.9 |        
    6658 | 2021-03-24 21:15:34 |          MASTER-IAC | (11h 49m 19.85s , +10d 13m 41.9s) |   C |    60 | 16.9 |        
    6738 | 2021-03-24 21:16:54 |          MASTER-IAC | (11h 32m 20.00s , +04d 07m 03.2s) |   C |    60 | 16.9 |        
    6738 | 2021-03-24 21:16:54 |          MASTER-IAC | (11h 24m 12.23s , +04d 12m 21.0s) |   C |    60 | 17.2 |        
    6818 | 2021-03-24 21:18:14 |          MASTER-IAC | (11h 00m 19.26s , -03d 52m 00.5s) |   C |    60 | 17.1 |        
    6867 | 2021-03-24 21:19:03 |         MASTER-SAAO | (11h 39m 13.31s , +08d 01m 44.8s) |   C |    60 | 18.7 |        
    6898 | 2021-03-24 21:19:34 |          MASTER-IAC | (11h 48m 19.18s , +04d 07m 39.8s) |   C |    60 | 16.8 |        
    6898 | 2021-03-24 21:19:34 |          MASTER-IAC | (11h 40m 11.52s , +04d 12m 58.0s) |   C |    60 | 16.6 |        
    6980 | 2021-03-24 21:20:56 |          MASTER-IAC | (11h 18m 18.50s , +06d 08m 30.8s) |   C |    60 | 17.3 |        
    6980 | 2021-03-24 21:20:56 |          MASTER-IAC | (11h 10m 08.87s , +06d 13m 47.8s) |   C |    60 | 17.0 |        
    7060 | 2021-03-24 21:22:16 |          MASTER-IAC | (11h 16m 19.83s , +04d 07m 30.4s) |   C |    60 | 17.3 |        
    7060 | 2021-03-24 21:22:16 |          MASTER-IAC | (11h 08m 11.73s , +04d 12m 46.4s) |   C |    60 | 17.0 |        
    7140 | 2021-03-24 21:23:36 |          MASTER-IAC | (11h 30m 36.02s , +00d 06m 36.3s) |   C |    60 | 16.8 |        
    7140 | 2021-03-24 21:23:36 |          MASTER-IAC | (11h 22m 29.49s , +00d 11m 51.7s) |   C |    60 | 16.8 |        
    7220 | 2021-03-24 21:24:56 |          MASTER-IAC | (11h 31m 06.30s , +02d 06m 42.9s) |   C |    60 | 16.9 |        
    7220 | 2021-03-24 21:24:56 |          MASTER-IAC | (11h 22m 59.36s , +02d 11m 59.2s) |   C |    60 | 17.1 |        
    7705 | 2021-03-24 21:33:01 |          MASTER-IAC | (11h 29m 49.06s , +12d 08m 16.1s) |   C |    60 | 17.2 |        
    7705 | 2021-03-24 21:33:01 |          MASTER-IAC | (11h 21m 28.38s , +12d 13m 26.5s) |   C |    60 | 17.1 |        
    7784 | 2021-03-24 21:34:20 |          MASTER-IAC | (11h 47m 03.05s , +02d 07m 39.6s) |   C |    60 | 16.8 |        
    7784 | 2021-03-24 21:34:20 |          MASTER-IAC | (11h 38m 54.06s , +02d 12m 50.7s) |   C |    60 | 16.7 |        
    7864 | 2021-03-24 21:35:40 |          MASTER-IAC | (11h 53m 34.87s , +08d 08m 39.2s) |   C |    60 | 17.1 |        
    7864 | 2021-03-24 21:35:40 |          MASTER-IAC | (11h 45m 21.05s , +08d 13m 52.3s) |   C |    60 | 17.0 |        
    7927 | 2021-03-24 21:36:43 |         MASTER-SAAO | (11h 44m 27.62s , +06d 01m 02.5s) |   C |    60 | 18.6 |        
    7944 | 2021-03-24 21:37:00 |          MASTER-IAC | (12h 04m 27.65s , +04d 07m 41.6s) |   C |    60 | 17.1 |        
    7944 | 2021-03-24 21:37:00 |          MASTER-IAC | (11h 56m 17.84s , +04d 12m 54.9s) |   C |    60 | 17.1 |        
    8007 | 2021-03-24 21:38:02 |         MASTER-SAAO | (11h 52m 20.58s , +05d 59m 57.1s) |   C |    60 | 18.6 |        
    8024 | 2021-03-24 21:38:20 |          MASTER-IAC | (11h 57m 31.44s , +10d 06m 40.4s) |   C |    60 | 17.1 |        
    8749 | 2021-03-24 21:50:25 |         MASTER-SAAO | (11h 34m 30.97s , +10d 00m 51.7s) |   C |    60 | 18.7 |        
    8829 | 2021-03-24 21:51:45 |         MASTER-SAAO | (11h 42m 31.07s , +10d 02m 23.3s) |   C |    60 | 18.7 |        
    8909 | 2021-03-24 21:53:05 |         MASTER-SAAO | (11h 41m 36.25s , +04d 00m 33.9s) |   C |    60 | 18.6 |        
    8989 | 2021-03-24 21:54:25 |         MASTER-SAAO | (11h 49m 35.94s , +04d 01m 51.2s) |   C |    60 | 18.7 |        
    9068 | 2021-03-24 21:55:44 |         MASTER-SAAO | (11h 18m 22.09s , +10d 01m 51.9s) |   C |    60 | 18.8 |        
    9947 | 2021-03-24 22:10:23 |         MASTER-SAAO | (11h 26m 35.53s , +10d 02m 53.7s) |   C |    60 | 18.9 |        
   10027 | 2021-03-24 22:11:43 |         MASTER-SAAO | (11h 40m 31.43s , +02d 01m 00.0s) |   C |    60 | 19.0 |        
   10107 | 2021-03-24 22:13:03 |         MASTER-SAAO | (11h 48m 31.53s , +02d 02m 29.7s) |   C |    60 | 18.8 |        
   10186 | 2021-03-24 22:14:22 |         MASTER-SAAO | (11h 39m 18.86s , +12d 01m 55.7s) |   C |    60 | 18.9 |        
   10266 | 2021-03-24 22:15:42 |         MASTER-SAAO | (11h 47m 25.79s , +12d 02m 49.2s) |   C |    60 | 18.7 |        
   10345 | 2021-03-24 22:17:01 |         MASTER-SAAO | (11h 02m 05.14s , -03d 57m 34.7s) |   C |    60 | 19.3 |        
   10504 | 2021-03-24 22:19:40 |         MASTER-SAAO | (11h 00m 53.05s , -01d 58m 28.1s) |   C |    60 | 19.1 |        
   10664 | 2021-03-24 22:22:20 |         MASTER-SAAO | (11h 35m 58.17s , +06d 01m 15.7s) |   C |    60 | 18.9 |        
   10753 | 2021-03-24 22:23:49 |         MASTER-SAAO | (11h 38m 53.92s , +08d 01m 04.8s) |   C |    60 | 19.0 |        
   10833 | 2021-03-24 22:25:09 |         MASTER-SAAO | (11h 52m 00.81s , +06d 01m 05.7s) |   C |    60 | 19.0 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210324C
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29723
SUBJECT: Fermi GRB 210324C: Global MASTER-Net observations report 
DATE:    21/03/24 22:30:17 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-SAAO robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 210324C ( Fermi GBM team, GCN 29718) errorbox  2759 sec after notice time and 2786 sec after trigger time at 2021-03-24 20:46:24 UT, with upper limit up to  17.1 mag. The observations began at zenith distance = 81 deg. The sun  altitude  is -48.8 deg. 

The galactic latitude b = -63 deg., longitude l = 263 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1576010

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

    2876 | 2021-03-24 20:46:24 |         MASTER-SAAO | (02h 45m 04.74s , -47d 04m 20.4s) |   C |   180 | 17.1 |        
    3076 | 2021-03-24 20:49:44 |         MASTER-SAAO | (02h 44m 59.67s , -47d 05m 16.2s) |   C |   180 | 16.7 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210323A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29724
SUBJECT: GRB 210323A: MASTER optical observation
DATE:    21/03/24 23:16:11 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

N.Tiurina, V. Lipunov, V.Kornilov, E.Gorbovskoy,P.Balanutsa,F.Balakin, 
V.Vladimirov, A.Kuznetsov,K.Zhirkov,D. Vlasenko, I.Gorbunov, D.Zimnukhov, 
V.Senik, A.Chasovnikov,A.Pozdnyakov,V.Topolev, D.Cheryasov(Lomonosov Moscow State University, SAI, Physics Department),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev (Irkutsk State University, API),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico FelixAguilar OAFA),
R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)

MASTER Global robotic net (MASTER-Net:http://observ.pereplet.ru Lipunov et al.,2010,Advances in Astronomy,2010,30L)
automatically started Swift  GRB 210323A (Gropp et al. GCN 29699, Ttrigger=22:02:18UT, 
https://gcn.gsfc.nasa.gov/other/210323A.gcn3)
optical observations at MASTER-Tunka (in ~100km of Mondy , Pozanenko et al. GCN 29708)
at 2021-03-23 22:03:12UT with 10s expositions by MASTER-600 twin robotic telescope
and by MASTER-VWFC (very wide field cameras)at sunrise.

The Sun altitude at MASTER-Tunka and Mondy was -9.6, see alert location 
and conditions of observation at 
http://observ.pereplet.ru/images/tunka2021-03-23-22-03-13.jpg (webcamera).

The distance to Sun of GRB coordinates was 49.6deg., that made 18.4m OT 
detection little likelihood for the telescopes at this location and at this time.

MASTER observed this alert's error-box also at
MASTER-Tavrida (2021-03-24 02:07:41 UT, with upper limit 18.2),
MASTER-IAC (2021-03-24 03:40:27 UT, Lipunov et al. 29702),
and MASTER-OAFA (started at 2021-03-24 09:40:18UT), 
see cover map, limits and altitudes at 
https://master.sai.msu.ru/site/master2/observ.php?id=1575256

Reduction and analyses will continue.
This message may be cited.


GRB_name: GRB210321A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29725
SUBJECT: GRB 210321A: OSN Upper Limit
DATE:    21/03/24 23:41:30 GMT
FROM:    Alexander Kann at IAA-CSIC  <kann@iaa.es>

D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, 
DARK/NBI), C. C. Thoene, M. Blazek, J. F. Agui Fernandez (all 
HETH/IAA-CSIC), and F. Aceituno (IAA-CSIC) report:

We observed the optical afterglow (Perri et al. GCN #29678; Siegel et 
al. GCN #29679; Butler et al. GCN #29680; Heintz et al. GCN #29684; Xin 
et al., GCN #29687; Pankov et al., GCNs #29689, #29692; Laporte et al., 
GCN #29697) of GRB 210321A (Swift detection: Dichiara et al., GCN 
#29677) with the 1.5m T150 telescope of the Observatorio de Sierra 
Nevada (OSN), Granada, Spain. Observations could not be taken due to 
high winds in the first night after the GRB. We obtained 11 x 180 s 
exposures in Rc starting at 2021-03-22 19:59:44.93 UT, before high winds 
shut the telescope down again. The afterglow is not detected in the 
combined image.

We determine an upper limit Rc > 23.3 mag (AB mag, vs. a nearby 
Pan-STARRS star converted to Rc following the Lupton transformations, 
then transformed back to AB mag) at 1.5437 days after the GRB.


GRB_name: GRB210323A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29726
SUBJECT: GRB 210323A: Insight-HXMT/HE detection
DATE:    21/03/25 03:15:20 GMT
FROM:    Y Q Zhang at IHEP  <yqzhang@ihep.ac.cn>

Y. Q. Zhang, C. Cai, J. C. Liu, Q. Luo, S. Xiao, 
W. C. Xue, Q. B. Yi, C. Zhengï¼ŒY. Huang, C. K. Li, 
G. Li, X. B. Li, J. Y. Liao, X. Y. Song, S. L. Xiong, C. Z. Liu, 
X. F. Li, Z. W. Li, Z. Chang, A. M. Zhang, Y. F. Zhang, 
X. F. Lu, C. L. Zou (IHEP), Y. J. Jin, Z. Zhang (THU), 
T. P. Li (IHEP/THU), F. J. Lu, L. M. Song, 
M. Wu, Y. P. Xu, S. N. Zhang (IHEP), 
report on behalf of the Insight-HXMT team:

At 2021-03-23T22:02:18.40 (T0), Insight-HXMT/HE detected 
GRB 210323A (trigger ID: HEB210323918) in a routine search of the data, 
which also triggered Swift/BAT (Gropp J.D. et al., GCN #29699) and 
Fermi/GBM (Hamburg R. et al., GCN #29709).

The Insight-HXMT/HE light curve mainly consists of a single 
pulse with a duration (T90) of 0.33 s measured from T0-0.03 s. 
The 1-ms peak rate, measured from T0+0.05 s, is 9821 cnts/sec. 
The total counts from this burst is 1842 counts. 
URL_LC: http://twiki.ihep.ac.cn/pub/HXMT/GRBList/HEB210323918_lc.jpg

All measurements above are made with the CsI detectors operating in the 
regular mode with the energy range of about 80-800 keV (deposited energy). 
Only gamma-rays with energy greater than about 200 keV can penetrate 
the spacecraft and leave signals in the CsI detectors installed inside 
of the telescope. 

Insight-HXMT is the first Chinese space X-ray telescope, which was 
funded jointly by the China National Space Administration (CNSA) and 
the Chinese Academy of Sciences (CAS). 
More information about it could be found at: 
http://www.hxmt.org.


GRB_name: GRB210324C
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29727
SUBJECT: IPN triangulation of GRB 210324C
DATE:    21/03/25 18:28:37 GMT
FROM:    Anna Ridnaia at Ioffe Institute  <ridnaia@mail.ioffe.ru>

K. Hurley, on behalf of the IPN,

I. G. Mitrofanov, D. V. Golovin, A. S. Kozyrev, M. L. Litvak,
and A. B. Sanin, on behalf of the HEND-Odyssey GRB team,

A. Ridnaia, S. Golenetskii, D. Frederiks, D. Svinkin,
A. Lysenko, and T. Cline on behalf of the Konus-Wind team,

A. Goldstein, M. S. Briggs, and C. Wilson-Hodge
on behalf of the Fermi GBM team,

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,

and

W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:

The long-duration GRB 210324C
(Fermi-GBM detection: The Fermi GBM team, GCN Circ. 29718;
BALROG localization: Kunzweileret et al., GCN Circ. 29719)
has been detected by Fermi (GBM trigger 638308803),
INTEGRAL (SPI-ACS), Konus-Wind, and Mars-Odyssey (HEND),
so far, at about 71998 s UT (19:59:58).

We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
 ---------------------------------------------
  RA(2000), deg                 Dec(2000), deg
 ---------------------------------------------
 Center:
   35.111 (02h 20m 27s) -48.606 (-48d 36' 21")
 Corners:
   43.843 (02h 55m 22s) -51.173 (-51d 10' 22")
   43.444 (02h 53m 46s) -51.998 (-51d 59' 54")
   27.400 (01h 49m 36s) -45.327 (-45d 19' 38")
   27.969 (01h 51m 53s) -44.554 (-44d 33' 15")
 ---------------------------------------------
The error box area is 10.7 sq. deg, and its maximum
dimension is 12.7 deg (the minimum one is 51 arcmin).
The Sun distance was 51 deg.

This box may be improved.

The IPN localization is consistent with, but reduces the area of, the
Fermi RoboBA and BALROG localizations (GCN Circ. 29718 and 29719).

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB210324_T72000/IPN/

The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.


GRB_name: GRB210324C
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29728
SUBJECT: Konus-Wind detection of GRB 210324C
DATE:    21/03/25 18:42:58 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

D. Frederiks, S. Golenetskii, A.Lysenko, A. Ridnaia,
D. Svinkin, A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The long GRB 210324C (IPN triangulation:  Hurley et al., GCN 29727)
triggered Konus-Wind (KW) at T0=72000.034 s UT (20:00:00.034).

The burst light curve shows a multi-peaked structure with the total 
duration of ~75 s.
The emission is seen up to ~10 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210324_T72000/

As observed by Konus-Wind, the burst had
a fluence of (7.0 Â± 0.6)x10^-5 erg/cm^2 and
a 64-ms peak energy flux, measured from T0+34.112,
of (3.4 Â± 0.4)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+65.024 s)
is best fit in the 20 keV - 20 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.51 (-0.10,+0.11),
the high energy photon index beta = -2.69 (-0.28,+0.18),
the peak energy Ep = 190 (-11,+12) keV,
chi2 = 97/97 dof.

The spectrum near the peak count rate (measured from T0+33.024
to T0+40.448 s) is best fit in the 20 keV - 20 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.56 (-0.15,+0.17),
the high energy photon index beta = -2.64 (-0.53,+0.24),
the peak energy Ep = 211 (-21,+26) keV,
chi2 = 108/97 dof.

All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.


GRB_name: GRB210326A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29730
SUBJECT: GRB 210326A: Fermi GBM Final Localization
DATE:    21/03/26 22:39:00 GMT
FROM:    Joshua Wood at MSFC/Fermi-GBM  <joshua.r.wood@nasa.gov>

The Fermi GBM team reports the detection of a likely SHORT GRB

At 01:22:24.93 UT on 26 Mar 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210326A (trigger 638414549.926002 / 210326057).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 58.0, Dec = +15.1 (J2000 degrees, equivalent to J2000 03h 52m, +15d 06'), with a statistical uncertainty of 39.2 degrees.

The angle from the Fermi LAT boresight is 69.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210326057/quicklook/glg_skymap_all_bn210326057.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210326057/quicklook/glg_healpix_all_bn210326057.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210326057/quicklook/glg_lc_medres34_bn210326057.gif


GRB_name: GRB210326A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29731
SUBJECT: GRB 210326A: Insight-HXMT/HE detection
DATE:    21/03/28 15:21:31 GMT
FROM:    Y Q Zhang at IHEP  <yqzhang@ihep.ac.cn>

Y. Q. Zhang, C. Cai, J. C. Liu, Q. Luo, S. Xiao, 
W. C. Xue, Q. B. Yi, C. Zhengï¼ŒY. Huang, C. K. Li, 
G. Li, X. B. Li, J. Y. Liao, X. Y. Song, S. L. Xiong, C. Z. Liu, 
X. F. Li, Z. W. Li, Z. Chang, A. M. Zhang, Y. F. Zhang, 
X. F. Lu, C. L. Zou (IHEP), Y. J. Jin, Z. Zhang (THU), 
T. P. Li (IHEP/THU), F. J. Lu, L. M. Song, 
M. Wu, Y. P. Xu, S. N. Zhang (IHEP), 
report on behalf of the Insight-HXMT team:

At 2021-03-26T01:22:24.93 (T0), Insight-HXMT/HE detected 
GRB 210326A (trigger ID: HEB210326057) in a routine search of the data, 
which also triggered Fermi/GBM (Fermi GBM team, GCN #29730).

The Insight-HXMT/HE light curve mainly consists of a single 
pulse with a duration (T90) of 0.17 s measured from T0-0.08 s. 
The 1-ms peak rate, measured from T0-0.08 s, is 5749 cnts/sec. 
The total counts from this burst is 733 counts. 
URL_LC: http://twiki.ihep.ac.cn/pub/HXMT/GRBList/HEB210326057_lc.jpg

All measurements above are made with the CsI detectors operating in the 
regular mode with the energy range of about 80-800 keV (deposited energy). 
Only gamma-rays with energy greater than about 200 keV can penetrate 
the spacecraft and leave signals in the CsI detectors installed inside 
of the telescope. 

Insight-HXMT is the first Chinese space X-ray telescope, which was 
funded jointly by the China National Space Administration (CNSA) and 
the Chinese Academy of Sciences (CAS). 
More information about it could be found at: 
http://www.hxmt.org.


GRB_name: GRB210328A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29732
SUBJECT: GRB 210328A: Fermi GBM Final Real-time Localization
DATE:    21/03/28 20:55:25 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 20:45:16 UT on 28 Mar 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210328A (trigger 638657121.97022 / 210328865).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 207.9, Dec = -8.6 (J2000 degrees, equivalent to J2000 13h 51m, -8d 35'), with a statistical uncertainty of 2.1 degrees.

The angle from the Fermi LAT boresight is 79.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210328865/quicklook/glg_skymap_all_bn210328865.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210328865/quicklook/glg_healpix_all_bn210328865.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210328865/quicklook/glg_lc_medres34_bn210328865.gif


GRB_name: GRB210328A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29733
SUBJECT: GRB 210328A: BALROG localization (Fermi Trigger  / GRB 210328865)
DATE:    21/03/28 21:17:20 GMT
FROM:    Jochen Greiner at MPE,Garching  <jcg@mpe.mpg.de>

B. Biltzinger, F. Kunzweiler, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
 at 20:45:16 on 28 March 2021 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).

The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 205.9+/-1.3 deg
Decl.(2000.0) = -11.4+/-1.5 deg
We estimate an additional systematic error of 1 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210328865/?data_version=h00

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/media/data/GRB210328865/data_files/210328_211506727701_GRB210328865_healpix_trigdat_h00.fits

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210328865/json

                        


GRB_name: GRB210324C
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29734
SUBJECT: GRB 210324C: AstroSat CZTI detection
DATE:    21/03/30 05:19:42 GMT
FROM:    Gaurav Waratkar at IIT Bombay  <gauravwaratkar24@gmail.com>

 P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), S. Gupta
(IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao
(IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI
collaboration:

Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al, 2020,
arxiv:2011.07067) showed detection of a long GRB 210324C, which was also
detected by Fermi-GBM (GCN #29718), and Konus-Wind (GCN #29728).

The source was clearly detected in the 20-200 keV energy range. The light
curve showed multiple peaks of emission with the strongest peak at
2021-03-24 20:00:36.50 UT. The measured peak count rate associated with the
burst is 214 (+47, -35) cts/s above the background in the combined data of
four quadrants, with a total 4856 (+784, -875) cts. The local mean
background count rate was 604 (+3, -3) cts/s. Using cumulative rates, we
measure a T90 of 63 (+14, -11) s.

CZTI GRB detections are reported regularly on the payload site at
http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led
consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and
PRL. The Indian Space Research Organisation funded, managed and facilitated
the project.


GRB_name: GRB210324A
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29735
SUBJECT: GRB 210324A: AstroSat CZTI detection
DATE:    21/03/30 11:05:00 GMT
FROM:    Gaurav Waratkar at IIT Bombay  <gauravwaratkar24@gmail.com>

P.  Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), S. Gupta
(IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao
(IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI
collaboration:

Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al, 2020,
arxiv:2011.07067) showed detection of a long GRB 210324A, which was also
detected by Fermi-GBM (GCN #29707).

The source was clearly detected in the 20-200 keV energy range. The light
curve showed multiple peaks of emission with the strongest peak at
2021-03-24 11:14:32 UT in two quadrants (out of four). The measured peak
count rate associated with the burst is 165 (+44, -21) cts/s above the
background in the combined data of four quadrants, with a total of 2373
(+286, -392) cts. The local mean background count rate was 490 (+3, -3)
cts/s. Using cumulative rates, we measure a T90 of 33 (+2, -5) s.

CZTI GRB detections are reported regularly on the payload site at
http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led
consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and
PRL. The Indian Space Research Organisation funded, managed and facilitated
the project.


GRB_name: GRB210330A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29736
SUBJECT: GRB 210330A: GECAM detection
DATE:    21/03/30 15:03:05 GMT
FROM:    Shaolin Xiong at IHEP  <xiongsl@ihep.ac.cn>

D. Y. Guo, Y. Huang, S. L. Xiong, S. Xiao, C. Cai, Y. Zhao, J. C. Liu,
Q. B. Yi, Y. Q. Zhang, W. C. Xue, C. Zheng, Z. W. Guo, X. Y. Zhao,
X. Y. Song, P. Wang, X. B. Li, W. X. Peng, R. Qiao, C. W. Wang,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, J. J. He,
B. Li, C. Li, C. Y. Li, J. H. Li, Q. X. Li, X. Q. Li, Y. G. Li, X. H. Liang,
J. Y. Liao, J. C. Liu, X. J. Liu, Y. Q. Liu, F. J. Lu, Q. Luo, X. Ma,
G. Ou,  D. L. Shi, J. Y. Shi, L. M. Song, G. X. Sun, X. L. Sun, Y. L. Tuo,
J. Z. Wang, X. Y. Wen, Y. B. Xu, Y. P. Xu, S. Yang, M. Yao, B. X. Zhang,
C. Y. Zhang, D. L. Zhang, Fan Zhang, Fei Zhang, H. M. Zhang, K. Zhang,
P. Zhang, S. N. Zhang, Z. Zhang, S. Y. Zhao, S. J. Zheng, X. Zhou (IHEP),
report on behalf of GECAM team:

During the commissioning phase, GECAM-B triggered a long burst,
GRB 210330A, at 2021-03-30T12:45:46.600 UTC (denoted as T0).

GECAM alert data was promptly downlinked to the ground through the
short message service of BeiDou Navigation Satellite System (BDS).
The time latency of the first BeiDou message relative to the trigger time
is about 1 minute.

According to the BDS alert data, this burst mainly consists of
a broad pulses with duration of about 20 s.

An automatic on-ground localization was calculated using the light curves
and counts spectrum in the BDS alert data.
Although the in-flight calibration of energy response and localization
has not been finalized yet, GECAM-B localized this burst to
the following position (J2000):
Ra: 164.3 deg Dec: -55.6 deg
Err: 5.1 deg (1-sigma, statistical only)
The current systematic error of location is estimated to be several degrees
which could be minimized by the ongoing calibration.

Given that the location is close to the galactic plane, we cannot rule out
the possibility that this burst originated from a galactic source.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_lc_grd_all_70807546.png

The GECAM preliminary location could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_skymap_70807546_V01.png

As the detailed science data are downloaded, all analyses would be improved.

Please note that all GECAM results here are preliminary. The final analysis
will be published in journal papers or GECAM online catalog.

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in
Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time),
which was funded by the Chinese Academy of Sciences (CAS).


GRB_name: GRB210328A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29737
SUBJECT: GRB 210328A: GECAM detection
DATE:    21/03/30 15:38:19 GMT
FROM:    Shaolin Xiong at IHEP  <xiongsl@ihep.ac.cn>

X. Y. Zhao, S. L. Xiong, X. Y. Song, D. Y. Guo, Y. Huang, S. Xiao,
C. Cai, Y. Zhao, J. C. Liu, Q. B. Yi, Y. Q. Zhang, W. C. Xue, C. Zheng,
Z. W. Guo,  P. Wang, X. B. Li, W. X. Peng, R. Qiao, C. W. Wang,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, J. J. He,
B. Li, C. Li, C. Y. Li, J. H. Li, Q. X. Li, X. Q. Li, Y. G. Li, X. H. Liang,
J. Y. Liao, J. C. Liu, X. J. Liu, Y. Q. Liu, F. J. Lu, Q. Luo, X. Ma,
G. Ou,  D. L. Shi, J. Y. Shi, L. M. Song, G. X. Sun, X. L. Sun, Y. L. Tuo,
J. Z. Wang, X. Y. Wen, Y. B. Xu, Y. P. Xu, S. Yang, M. Yao, B. X. Zhang,
C. Y. Zhang, D. L. Zhang, Fan Zhang, Fei Zhang, H. M. Zhang, K. Zhang,
P. Zhang, S. N. Zhang, Z. Zhang, S. Y. Zhao, S. J. Zheng, X. Zhou (IHEP),
report on behalf of GECAM team:

During the commissioning phase, GECAM-B triggered by a long burst,
GRB 210328A, at 2021-03-28 20:45:17.900 UTC (T0), which was also detected
by Fermi/GBM (GCN #29732)

According to the GECAM-B light curves in about 20 keV - 500 keV,
this burst mainly consists of a broad pulse with duration of about 12 s.

Spectral evolution is clearly seen during the burst, and the emissions
in low energies last longer than that in high energies.

Although the in-flight calibration of energy response and localization
has not been finalized yet, GECAM-B localized this burst to the
following position (J2000):
Ra: 201.9 deg Dec: -2.6 deg
Err: 3.4 deg (1-sgima, statistical only)

The current systematic error of location is estimated to be several degrees
which could be minimized by the ongoing calibration.

GECAM location is consistent with the Fermi/GBM and BALROG positions
within the error.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/multiLCvsE_tn210328_204626.pdf

The GECAM preliminary location could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/tn210328_204626_locSatB.pdf

Please note that all GECAM results here are preliminary. The final analysis
will be published in journal papers or GECAM online catalog.

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in
Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time),
which was funded by the Chinese Academy of Sciences (CAS).


GRB_name: GRB210330A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29738
SUBJECT: GRB 210330A: MASTER optical observation 
DATE:    21/03/30 21:27:39 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, A.Chasovnikov, F.Balakin, V.Kornilov, E.Gorbovskoy,P.Balanutsa, V.Vladimirov, A.Kuznetsov,K.Zhirkov,D. Vlasenko, 
N.Tiurina, I.Gorbunov, D.Zimnukhov, V.Senik, V.Topolev, D.Cheryasov (Lomonosov Moscow State University, SAI, Physics Department),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev (Irkutsk State University, API),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico FelixAguilar OAFA),
R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)

MASTER Global robotic net (MASTER-Net:http://observ.pereplet.ru Lipunov et al.,2010,Advances in Astronomy,2010,30L)
started GECAM  GRB 210330A (D.Y.Guo et al. GCN 29739, Ttrigger=12:45:46.600 UTC, R.A.Dec.: 164.3d,-55.6d, er.-b.=5.1d) 
optical observations at MASTER-SAAO (located in South African Astronomical Observatory) 
17496 sec after trigger time at 2021-03-30 17:37:23 UT at sunset, with 
upper limit up to  18.7 mag.

Observations started at zenith distance = 43 deg. The sun  altitude was -13.6 deg.

The galactic latitude b =  4 deg., longitude l = 288 deg.

Real time updated cover map and OT,that can be discovered, will be available here:
https://master.sai.msu.ru/site/master2/observ.php?id=1580304

There are the following upper limits of the first images

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
    17587 | 2021-03-30 17:37:23 |         MASTER-SAAO | (10h 57m 26.66s , -55d 35m 44.3s) |   C |   180 | 18.7 |
    17787 | 2021-03-30 17:40:43 |         MASTER-SAAO | (10h 57m 26.36s , -55d 34m 44.9s) |   C |   180 | 18.6 |
    17986 | 2021-03-30 17:44:02 |         MASTER-SAAO | (11h 05m 32.80s , -55d 35m 42.8s) |   C |   180 | 18.6 |
Filter C is a clear (unfiltred) band.


The observation and reduction will continue.
The message may be cited.


GRB_name: GRB210401A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29739
SUBJECT: GRB 210401A: Fermi GBM Final Real-time Localization
DATE:    21/04/01 23:27:12 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 23:17:04 UT on 1 Apr 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210401A (trigger 639011829.029182 / 210401970).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 263.1, Dec = -31.6 (J2000 degrees, equivalent to J2000 17h 32m, -31d 36'), with a statistical uncertainty of 1.8 degrees.

The angle from the Fermi LAT boresight is 98.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210401970/quicklook/glg_skymap_all_bn210401970.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210401970/quicklook/glg_healpix_all_bn210401970.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210401970/quicklook/glg_lc_medres34_bn210401970.gif


GRB_name: GRB210401A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29740
SUBJECT: Fermi GRB 210401A: Global MASTER-Net observations report 
DATE:    21/04/02 21:00:17 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-SAAO robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 210401A ( Fermi GBM team, GCN 29739) errorbox  77156 sec after notice time and 77165 sec after trigger time at 2021-04-02 20:43:09 UT, with upper limit up to  17.2 mag. The observations began at zenith distance = 80 deg. The sun  altitude  is -51.3 deg. 

The galactic latitude b =  0 deg., longitude l = 357 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1581695

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   77256 | 2021-04-02 20:43:09 |         MASTER-SAAO | (17h 29m 04.89s , -34d 09m 47.6s) |   C |   180 | 17.2 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210402A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29743
SUBJECT: GRB 210402A: Swift detection of a burst
DATE:    21/04/02 22:30:12 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

K. L. Page (U Leicester), S. D. Barthelmy (GSFC),
F. E. Marshall (NASA/GSFC) and D. M. Palmer (LANL) report on behalf of
the Neil Gehrels Swift Observatory Team:

BAT has triggered on a new GRB 210402A (Trigger #1040123) causing 
Swift to slew to the location and make follow-up observations.  
Due to a ground pass at the time of the GRB, no precise trigger 
time, location, or light curve data is immediately available. 
These details will be given in a later circular. 

We note that Fermi triggered on a GRB at around the same time at a 
consistent location (Fermi Trigger #639093861) confirming its GRB status. 

Using promptly downlinked data we find a bright, uncatalogued X-ray
source located at RA, Dec 198.25866, 44.51291 which is equivalent to:
   RA(J2000)  = 13h 13m 02.08s
   Dec(J2000) = +44d 30' 46.5"
with an uncertainty of 3.5 arcseconds (radius, 90% containment). This
position may be improved as more data are received; the latest position
is available at https://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 1.51
x 10^20 cm^-2 (Willingale et al. 2013). 

The initial flux in the 2.5 s image was 1.31e-08 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of nominal 150 seconds with the
White  filter. No credible afterglow candidate has  been found in the
initial data products. The 2.7'x2.7' sub-image covers 100% of  the XRT
error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
No correction has been made for the extinction in the Milky Way. 

Burst Advocate for this burst is K. L. Page (klp5 AT leicester.ac.uk). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB210401A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29744
SUBJECT: Konus-Wind detection of GRB 210401A
DATE:    21/04/02 23:19:00 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

D. Svinkin, D. Frederiks, S. Golenetskii, A.Lysenko,
A. Ridnaya, A. Tsvetkova,  M. Ulanov, and T. Cline, report:

The long-duration GRB 210401A (Fermi-GBM detection: The Fermi GBM team,
GCN Circ. 29739) was detected by Konus-Wind (KW) in the waiting mode.

A Bayesian block analysis of the KW waiting mode data in
the 20-1500 keV band reveals a count rate increase over background
in the interval from ~T0-500 s to ~T0+340 s,
where T0 = T0(GBM) = 83824 (23:17:04) UT.
The total duration of ~840 s makes this burst an ultra-long GRB candidate.
On the other hand, the proximity of the burst localization (GCN 29739)
to the Galactic center may suggest that the burst is a galactic transient.
The KW light curve of this burst is available at
http://www.ioffe.ru/LEA/GRBs/GRB210401A/

Modeling the KW 3-channel time-integrated spectrum
(measured from T0-499.335 s to T0+339.705 s)
by a power law with exponential cutoff (CPL) model
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -1.40(-0.10,+0.12) and Ep = 240(-35,+45) keV.

A CPL fit to the spectrum near the peak count rate,
measured from T0+248.441 s to T0+254.329 s, gives
alpha -1.25(-0.12,+0.13), and Ep = 413(-78,+122) keV.

In the 10 keV -10 MeV band, the total burst fluence
is (1.46 +/- 0.18)x10^-4 erg/cm^2, and the 2.944 s peak energy flux,
measured in the interval starting from T0+248.441 s,
is (1.73 +/- 0.22)x10^-6 erg/cm^2.

All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.

[GCN OPS NOTE(03apr21),  Per author's request, the typo in the SUBJECT:-line
was changed from 210104A to 210401A.]


GRB_name: GRB210402A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29745
SUBJECT: GRB 210402A: NOT optical upper limits
DATE:    21/04/03 02:55:03 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

Z.P. Zhu (NAOC, HUST), D. Xu (NAOC), L. Izzo (DARK/NBI), J. Martikainen 
(NOT) report on behalf of a larger collaboration:

We observed the field of GRB 210402A (Page et al., GCN 29743) using the 
Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. 
Observations started at 00:19:22 UT on 2021-04-03, i.e., 2.23 hr after 
the burst, and we obtained 3x300 s and 5x200 s frames in the SDSS r- and 
z- filters, respectively.

Preliminary analysis reveals that no optical transient is detected in 
our stacked images within or at the edge of the current XRT error circle 
(3.5 arcsec; Page et al., GCN 29743), down to limiting magnitudes of r ~ 
24.6 and z ~ 23.2, calibrated with nearby PanSTARRS stars.

Compared with the bright X-ray afterglow and no much X-ray column 
density excess, it may indicate that the burst is a high-redshift one.

NIR follow-ups are strongly encouraged.


GRB_name: GRB210328A
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29746
SUBJECT: GRB 210328A: AstroSat CZTI detection
DATE:    21/04/03 04:49:11 GMT
FROM:    Gaurav Waratkar at IIT Bombay  <gauravwaratkar24@gmail.com>

P.  Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), S. Gupta
(IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao
(IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI
collaboration:

Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al, 2020,
arxiv:2011.07067) showed detection of a long GRB 210328A, which was also
detected by Fermi-GBM (GCN #29732, #29733) and GECAM-B (GCN #29737).

The source was clearly detected in the 20-200 keV energy range. The light
curve showed multiple peaks of emission with the strongest peak at
2021-03-28 20:45:21.5 UT. The measured peak count rate associated with the
burst is 338 (+48, -45) cts/s above the background in the combined data of
four quadrants, with a total of 4242 (+496, -511) cts. The local mean
background count rate was 528 (+2, -3) cts/s. Using cumulative rates, we
measure a T90 of 39 (+10, -13) s.

It was also clearly detected in the CsI anticoincidence (Veto) detector in
the 100-500 keV energy range. The light curve showed multiple peaks of
emission with the strongest peak at 2021-03-28 20:45:18.1 UT. The measured
peak count rate is 296 (+85, -28) cts/s above the background in the
combined Veto data of four quadrants, with a total of 3378 (+447, -604)
cts. The local mean background count rate was 1740 (+6, -5) cts/s. We
measure a T90 of 18 (+3, -4) s from the cumulative Veto light curve.

CZTI GRB detections are reported regularly on the payload site at
http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led
consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and
PRL. The Indian Space Research Organisation funded, managed and facilitated
the project.


GRB_name: GRB210402A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29747
SUBJECT: GRB 210402A: Montarrenti Observatory upper limit
DATE:    21/04/03 07:17:41 GMT
FROM:    Simone Leonini at Monarrenti Obs  <s.leonini@iol.it>

Simone Leonini, M. Conti, P. Rosi and L.M. Tinjaca Ramirez (Montarrenti Observatory, Siena, Italy) report:

We observed the field of GRB210402A (Swift trigger 1040123, Fermi trigger 639093861, K.L. Page et al., GCN Circ. 29743) with the automatic 0.53m RC telescope + U47 detector at Montarrenti Observatory (Siena, Italy, IAU code C88).

The observations were started at 2021-04-02 22:48:18 UT (18 minutes post-burst) stacking 4 unfiltered CCD exposures of 40s each.

We have not found optical transient within the error-box given.
Mag. upper limit R = 20.10+/-0.19

Magnitudes were obtained using Astrometrica software using USNO-B1 catalogue and are not corrected for galactic extinction.


GRB_name: GRB210403A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29748
SUBJECT: GRB 210403A: Swift detection of a burst
DATE:    21/04/03 08:40:22 GMT
FROM:    Kim Page at U.of Leicester  <klp5@leicester.ac.uk>

K. L. Page (U Leicester) and A. Y. Lien (GSFC/UMBC) report on behalf
of the Neil Gehrels Swift Observatory Team:

At 08:27:13 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210403A (trigger=1040345).  Swift did not slew immediately 
to the burst due to an observing constraint. 
The BAT on-board calculated location is 
RA, Dec 2.767, -32.999 which is 
   RA(J2000) = 00h 11m 04s
   Dec(J2000) = -32d 59' 56"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multi-peaked
structure with a duration of about 140 sec.  The peak count rate
was ~1200 counts/sec (15-350 keV), at ~0 sec after the trigger. 

Due to a Sun observing constraint, Swift cannot slew to the BAT
position until 21:34 UT on 2021 April 14. There will thus be no XRT or
UVOT data for this trigger before this time. 

Burst Advocate for this burst is K. L. Page (klp5 AT leicester.ac.uk). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB210330A
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29749
SUBJECT: GRB 210330A: AstroSat CZTI detection
DATE:    21/04/03 11:10:00 GMT
FROM:    Gaurav Waratkar at IIT Bombay  <gauravwaratkar24@gmail.com>

 P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), S. Gupta
(IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao
(IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI
collaboration:

Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al, 2020,
arxiv:2011.07067) showed detection of a long GRB 210330A, which was also
detected by GECAM (GCN #29736).

The source was clearly detected in the 20-200 keV energy range. The light
curve showed multiple peaks of emission with the strongest peak at
2021-03-30 12:45:46.50 UT. The measured peak count rate associated with the
burst is 262 (+45, -46) cts/s above the background in the combined data of
four quadrants, with a total 1367 (+248, -267) cts. The local mean
background count rate was 510 (+3, -3) cts/s. Using cumulative rates, we
measure a T90 of 13 (+2, -7) s.

CZTI GRB detections are reported regularly on the payload site at
http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led
consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and
PRL. The Indian Space Research Organisation funded, managed and facilitated
the project.


GRB_name: GRB210402A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29750
SUBJECT: GRB 210402A: Swift-XRT refined Analysis
DATE:    21/04/03 12:53:41 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans (U. Leicester), M. Capalbi (INAF-IASFPA), M. Perri (SSDC &
INAF-OAR), V. D'Elia (SSDC & INAF-OAR), J.A. Kennea (PSU), A.
Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), J.P. Osborne (U.
Leicester) and K.L. Page report on behalf of the Swift-XRT team:

We have analysed 6.0 ks of XRT data for GRB 210402A (Page et al. GCN
Circ. 29743), from 160 s to 46.0 ks after the  BAT trigger. The data
comprise 1.1 ks in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. Using 1629 s of PC mode data and 3 UVOT
images, we find an enhanced XRT position (using the XRT-UVOT alignment
and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec =
198.25927, +44.51454 which is equivalent to:

RA (J2000): 13h 13m 02.22s
Dec(J2000): +44d 30' 52.3"

with an uncertainty of 2.0 arcsec (radius, 90% confidence).

The late-time light curve (from T0+5.4 ks) can be modelled with a
power-law decay with a decay index of alpha=1.03 (+0.21, -0.27).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.811 (+0.027, -0.026). The
best-fitting absorption column is  3.25 (+/-0.13) x 10^21 cm^-2, in
excess of the Galactic value of 1.5 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.09 (+0.20, -0.19)
and a best-fitting absorption column of 3.2 (+/-0.8) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.6 x 10^-11 (5.6 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      3.2 (+/-0.8) x 10^21 cm^-2
Galactic foreground: 1.5 x 10^20 cm^-2
Excess significance: 6.5 sigma
Photon index:      2.09 (+0.20, -0.19)

If the light curve continues to decay with a power-law decay index of
1.03, the count rate at T+24 hours will be 0.017 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.0 x
10^-13 (9.4 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01040123.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210402A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29752
SUBJECT: GRB 210402A: DDOTI Upper Limits
DATE:    21/04/03 15:04:05 GMT
FROM:    Alan M Watson at UNAM  <alan@astro.unam.mx>

Nat Butler (ASU), Alan M. Watson (UNAM), Rosa L. Becerra (UNAM), Simone Dichiara
(GSFC/UMD), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), OcÃ©lotl Lopez
(UNAM), Diego Gonzalez (UNAM), Margarita Pereyra (UNAM), Srihari Ravi (ASU), and
Eleonora Troja (GSFC/UMD) report:

We observed the field of the Swift/BAT GRB 210402A (Page et al., GCN Circ.
29743) with the DDOTI wide-field imager at the Observatorio AstronÃ³mico Nacional
on Sierra San Pedro Martir (http://ddoti.astroscu.unam.mx) from 2021-04-03 02:52
UTC to 2021-04-03 12:18 UTC (from 4.8 to 14.2 hours after the trigger).

We observed a region covering aproximately 7 degrees in RA and 10 degrees in
declination (about 70 square degrees), including the XRT position in the w
filter, and obtained 23ks of exposure. We calibrated our images against the
APASS catalog.

Compared to the USNO-B1, Pan-STARRS DR1, and APASS DR10 catalogs, we do not
detect a source at the X-ray position to a 3-sigma limiting magnitude of w =
23.2.

Our non-detection is consistent with the non-detections reported by Zhu et al.
(GCN Circ. 29745) and Leonini et al. (GCN Circ. 29747).

We thank the staff of the Observatorio Astronomico Nacional in San Pedro Martir.


GRB_name: GRB210402A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29753
SUBJECT: GRB 210402A: LBT observations
DATE:    21/04/03 18:51:46 GMT
FROM:    Andrea Rossi at INAF  <andrea.rossi@inaf.it>

A Rossi (INAF-OAS) report on behalf of the CIBO collaboration:

We observed the field of GRB 210402A (Page et al., GCN 29743) 
simultaneously in the r' and z' bands with the LBC imager mounted on LBT 
(Mt Graham, AZ, USA). We obtained 20min of imaging on 2021-04-03 at 
mid-time 05:33:00 UT, 0.305 days days after the swift GCN. Observations 
were performed under an average seeing of ~1.4".

Within the refined XRT position (Evans etal., GCN 29750) we detect an 
extended source in both bands at position (J2000)
RA =13:13:02.04
DEC=+44:30:52.7
and preliminary magnitudes (AB system),
r=23.9+-0.2
z=23.1+-0.3
calibrated against SDSS field stars.

We note that a second source with r=23.4+-0.1 lies at position (J2000)
RA =13:13:02.46
DEC=+44:30:50.3
which is at south-east and outside the XRT error circle, and thus 
unlikely associated eith the GRB.

Moreover, this second source is already present (but it is very faint) 
in archival Pan-STARRS images, while the first one is beyond the survey 
limits. We note that, assuming that both are galaxies, the first one is 
more likely to be the host galaxy because of its brightness and distance 
which result in a smaller probability of chance association.

In both cases we cannot exclude that the afterglow is still contributing 
to the brightness of this sources. Further observations are necessary to 
assess their variability.

We acknowledge the excellent support from the LBTO and LBT-INAF staff, 
particularly B. Rothberg, J. Williams, and F. Cusano, in obtaining these 
observations.


GRB_name: GRB210403A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29754
SUBJECT: GRB 210403A: Swift-BAT refined analysis
DATE:    21/04/03 20:57:12 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

H. A. Krimm (NSF), S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL), (i.e. the Swift-BAT team):
 
Using the data set from T-61 to T+242 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210403A (trigger #1040345)
(K.Page, et al., GCN Circ. 29748).  The BAT ground-calculated position is
RA, Dec = 2.813, -33.024 deg which is 
   RA(J2000)  =  00h 11m 15.2s 
   Dec(J2000) = -33d 01' 27.2" 
with an uncertainty of 2.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 80%.
 
The lightcurve has multiple peaks starting at T-40 sec and ending at T+140 sec.
T90 (15-350 keV) is 168.3 +- 9.2 sec (estimated error including systematics).
 
The time-averaged spectrum from T-41.51 to T+137.18 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 0.93 +- 0.52, 
and Epeak of 37.4 +- 4.8 keV (chi squared 52.21 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 2.7 +- 0.2 x 10^-06 erg/cm2
and the 1-sec peak flux measured from T+0.18 sec in the 15-150 keV band is
1.1 +- 0.2 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 2.13 +- 0.10 (chi squared 73.02 for 57 d.o.f.).  All the quoted errors
are at the 90% confidence level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1040345/BA/


GRB_name: GRB210402A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29755
SUBJECT: GRB 210402A: BOOTES-network early optical upper limit
DATE:    21/04/03 21:43:03 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

Y.-D. Hu, E. Fernandez-Garcia, A. J. Castro-Tirado, M. D. Caballero-Garcia, M. A. Castro Tirado (IAA-CSIC), C. Perez del Pulgar, A. Castellon, I. Carrasco (Univ. de Malaga), R. Fernandez-Munoz (IHSM/UMA-CSIC), M. Jelinek (ASU-CAS), S. Guziy (Univ. of Nikolaev) and D. R. Xiong, Y. F. Fan, J. M. Bai, C. J. Wang, Y. X. Xin, X. H. Zhao (Yunnan Observatories of CAS), on behalf of a larger collaboration, report:

Following the detection of GRB 210402A by Swift (Page et al. GCNC 29743), the 0.6m BOOTES-4/MET robotic telescope at Lijiang Astronomical Observatory (China) automatically followed up this event at 22:10:15 UT (~ 19 s after notice) gathering images (60 s exposure time, clear filter). Furthermore, the 0.6 m BOOTES-2/TELMA robotic telescope at IHSM La Mayora (UMA-CSIC) in Algarrobo Costa (Malaga, Spain) also responded to this event, with the first image (60 s exposure, clear filter) obtained at 22:12:04 UT on April 2 (~ 2 min after notice).

In any case,  no optical transient is detected down to 19.2 and 18.9 mag respectively within the Swift/XRT error region (Evans et al, GCNC 29750). These two non-detections are consistent with the limits reported by MASTER (Lipunov et al, GCNC 29741), Swift/UVOT (Page et al. GCNC 29743), Montarrenti (Leonini et al. GCNC 29747), NOT (Zhu et al, GCNC 29745) and DDOTI (Butler et al, GCNC 29752).

We thank the staff at both La Mayora and Lijiang Astronomical Observatory for their excellent support.


GRB_name: GRB210402A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29757
SUBJECT: GRB 210402A: NOT optical afterglow candidate
DATE:    21/04/04 08:23:51 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

D. Xu (NAOC), Z.P. Zhu (NAOC,HUST), D. B. Malesani (DTU Space) report on 
behalf of a larger collaboration:

We reanalysed our previously reported NOT data (Zhu et al., GCN 29745), 
given that the position of the Swift/XRT error circle has significantly 
changed (Page et al., GCN 29743; Evans et al., GCN 29750).

An optical source, S1, is detected at the western edge of the refined 
XRT error circle (Evans et al., GCN 29750) at coordinates: R.A.(J2000) 
=13:13:02.04 and Dec.(J2000)=+44:30:52.69, with r = 24.0 +/- 0.2 and z = 
22.6 +/- 0.3, calibrated with nearby PanSTAR stars. S1 is also detected 
by the LBT observations (Rossi, GCN 29753), and the magnitudes are 
consistent with each other with 1sigma error. In addition, the GRB field 
is covered by the Legacy Survey, and forced aperture photometry of the 
S1 position gives r ~ 24.5 and z ~ 23.3, both fainter than the NOT 
measurements. Thus, S1 is the optical afterglow candidate of the burst.

A second source, S2, is detected at the south-east and outside of the 
refined XRT error circle at coordinates: R.A.(J2000) =13:13:02.45 and 
Dec.(J2000)=+44:30:50.31, as pointed by the LBT observations. It has r 
= 23.5 +/- 0.1 and z = 23.0 +/- 0.2 from the NOT images, and again no 
r-band variability between the NOT and LBT epochs. Moreover, forced 
aperture photometry of the S2 position from the Legacy Survey gives r ~ 
23.6 and z ~ 23.0, being consistent with the NOT measurements. Thus, 
we're inclined to conclude that S2 is unlikely the optical afterglow of 
the burst.

Further observations are planned to asses the brightness variability.


GRB_name: GRB210401A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29758
SUBJECT: GRB 210401A: GECAM detection
DATE:    21/04/04 15:01:13 GMT
FROM:    Wangchen Xue at IHEP  <xuewc@ihep.ac.cn>

W. C. Xue, S. L. Xiong, X. Y. Song, Y. Huang, S. Xiao, C. Cai, Y. Zhao, 
J. C. Liu, Q. B. Yi, Y. Q. Zhang, C. Zheng, Z. W. Guo, X. Y. Zhao, 
P. Wang, X. B. Li, W. X. Peng, R. Qiao, D. Y. Guo, C. W. Wang,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, J. J. He,
B. Li, C. Li, C. Y. Li, J. H. Li, Q. X. Li, X. Q. Li, Y. G. Li, X. H. Liang,
J. Y. Liao, J. C. Liu, X. J. Liu, Y. Q. Liu, F. J. Lu, Q. Luo, X. Ma,
G. Ou,  D. L. Shi, J. Y. Shi, L. M. Song, G. X. Sun, X. L. Sun, Y. L. Tuo,
J. Z. Wang, X. Y. Wen, Y. B. Xu, Y. P. Xu, S. Yang, M. Yao, B. X. Zhang,
C. Y. Zhang, D. L. Zhang, Fan Zhang, Fei Zhang, H. M. Zhang, K. Zhang,
P. Zhang, S. N. Zhang, Z. Zhang, S. Y. Zhao, S. J. Zheng, X. Zhou (IHEP),
report on behalf of GECAM team:

During the commissioning phase, GECAM-B triggered a very long burst,
GRB 210401A, at 2021-04-01 23:17:08.000 UTC (T0), which was also detected
by Fermi/GBM (GCN #29739) and Konus-Wind (GCN #29744).

According to the GECAM-B light curves in about 10 keV - 500 keV, 
this burst mainly consists of multiple pulses with duration of about 800 s.

Although the in-flight calibration of energy response and localization
has not been finalized yet, GECAM-B localized this burst to the 
following position (J2000):
Ra: 275.3 deg Dec: -29.2 deg 
Err: 5.8 deg (1-sigma, statistical only) 

The current systematic error of location is estimated to be several degrees
which could be minimized by the ongoing calibration. 

Given that the location is close to the galactic plane, we cannot rule out
the possibility that this burst originated from a galactic source. 

GECAM location is consistent with that of Fermi/GBM within the error.

The GECAM light curve could be found here: 
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/71018228.0energys.pdf

The GECAM preliminary location could be found here:  
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/tn210401_232014_locationSatB_map.pdf

Please note that all GECAM results here are preliminary. The final analysis
will be published in journal papers or GECAM online catalog.

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in
Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time),
which was funded by the Chinese Academy of Sciences (CAS).


GRB_name: GRB210207B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29759
SUBJECT: GRB 210207B: Prompt and very late time observations with HCT.
DATE:    21/04/04 16:50:36 GMT
FROM:    Firoza Sutaria at Indian Inst. of Astrophysics  <fsutaria@iiap.res.in>

F. Sutaria (IIA, Bangalore, India) and A. Ray (TIFR /HBCSE, Mumbai, 
India) report on the observations of the optical counterpart of GRB 
210207B (Lien et al., GCN #29420; Strausbaugh, R, GCN #29441 and 
references therein) taken with the Himalyan Chandra telescope (HCT) on 
two epochs.

The first observation was on MJD 59254.91163194 -- i.e 48.0103 hr after 
the Swift/BAT trigger.  The field of the GRB was observed in the Bessel 
R filter.  We stacked 12 frames to achieve a total exposure time of 570 
s. The photometry  was carried out using standard  IRAF utilities for 
faint objects in relatively uncrowded fields. The instrumental 
magnitudes were calibrated against photometric  standards in the field 
of PG0918+029, taken on the same and on the previous night, resulting in 
an average atmospheric extinction coefficient of 0.087(\pm 0.0208) /mag 
in this filter. At the position of the GRB  (18:02:32.40 +53:40:56.0) we 
find a faint optical source with apparent magnitude R=22.0 \pm 0.1, 
uncorrected for galactic extinction.


We observed the same field once again on 17th Mar. 2021 (MJD 
59290.91730324), in the same filter. A stacked exposure of 10 frames 
leading to a total exposure time of 600s  did not reveal any source at 
the location of the GRB, down to a 3-sigma limiting magnitude of R= 
23.66. We thus conclude that there was no contribution from the host 
galaxy in the previous detection. Our results are also tabulated below.

-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
MJD            Filter  Detected?         Magnitude
                                          (uncorrected for galactic 
extinction)
-------------------------------------------------------------------------------
59254.9116        R        Yes           22.0 \pm 0.1
59290.9173        R        No.           < 23.66 (3-sigma)
-------------------------------------------------------------------------------

We note that the galactic extinction for the CTIO R filter in this 
direction is estimated at A_R = 0.087 mag [Schlafly E. F. & Finkbeiner 
D., 2011, ApJ, 737, 103], based on a SDSS dust map. However, the IRAS 
and COBE/DIRBE survey  [D.J. Schlegel, D.P. Finkbeiner, & M. Davis, 
1998, ApJ, 500, 525] sets it at A_R=0.109 mag.

This GCN may be cited.

We thank the staff of IAO, Hanle and CREST, Hosakote, that made these 
observations possible. The facilities at IAO and CREST are operated by 
the Indian Institute of Astrophysics, Bangalore.


GRB_name: GRB210402A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29761
SUBJECT: GRB 210402A: Swift-BAT refined analysis
DATE:    21/04/04 20:51:19 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC),
H. A. Krimm (NSF), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), K. L. Page (U Leicester),
D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-60 to T+243 sec from the recent telemetry
downlink,
we report further analysis of BAT GRB 210402A (trigger #1040123)
(Page et al., GCN Circ. 29743).  The BAT ground-calculated position is
RA, Dec = 198.265, 44.510 deg which is
   RA(J2000)  =  13h 13m 03.7s
   Dec(J2000) = +44d 30' 36.1"
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 69%.

The mask-weighted light curve shows a multi-peaked structure that
starts at ~T-50 s and ends at ~T+310 s. The main peak occurs
at ~T+174 s. T90 (15-350 keV) is 238.7 +- 18.8 sec
(estimated error including systematics).

The time-averaged spectrum from T-51.60 to T+310.20 sec is best fit by a
power law
with an exponential cutoff.  This fit gives a photon index 1.49 +- 0.27,
and Epeak of 63.6 +- 22.9 keV (chi squared 58.82 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 8.6 +- 0.4 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+173.53 sec in the 15-150 keV band is
1.6 +- 0.2 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.87 +- 0.06 (chi squared 65.10 for 57 d.o.f.).  All the quoted errors
are at the 90% confidence level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1040123/BA/

[GCN OPS NOTE(04apr21): The word "DRAFT:" was removed fron the SUBJECT line.
The body of the Circular does contain the author's final text.]


GRB_name: GRB210402A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29762
SUBJECT: GRB 210402A: Further NOT optical observations
DATE:    21/04/05 15:18:50 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

Z.P. Zhu (NAOC,HUST), D. Xu (NAOC), D. B. Malesani (DTU Space) report on 
behalf of a larger collaboration:

We continued to observe the field of GRB 210402A (Page et al., GCN 
29743) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC 
camera. We obtained 9x360 s frames in the Sloan r-filter, starting at 
23:04:56 UT on 2021-04-04, i.e., 2.04 days after the burst.

The optical afterglow candidate, S1, (Xu et al. GCN 29757, see also 
Rossi et al., GCN 29753) is still detected in the stacked image. S1 now 
has r = 24.3 +/- 0.1, calibrated with nearby Pan-STARRS stars, while it 
had r = 24.0 +/- 0.2 in the last NOT epoch. The magnitudes are basically 
consistent with each other within 1\sigma error, although there might be 
slight decay, which indicates that S1 has been dominated by the 
potential host galaxy since the first NOT epoch.

Meanwhile, the unlikely optical afterglow source, S2, is well detected 
in the stacked image with r= 23.5 +/- 0.1, the same as the last NOT 
epoch. We thus conclude that S2 is not associated to the GRB.


GRB_name: GRB210402A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29763
SUBJECT: GRB 210402A: Fermi GBM detection
DATE:    21/04/05 20:19:05 GMT
FROM:    Oliver J Roberts at USRA/NASA  <oliver.roberts@nasa.gov>

O.J. Roberts (USRA/MSFC) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 22:04:16.98 UT on the 2nd April 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210402A (trigger 639093861 / 210402920), which was also
detected by the Swift/BAT (Page et al. 2021, GCN 29743). The GBM on-ground 
location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 44 degrees.

The GBM light curve consists of several broad, faint peaks, including emission 
about 60 s prior to the trigger time. The T90 duration of the event is about 
76 s (50-300 keV). The time-averaged spectrum from T0-60 s to T0+16 s is adequately 
fit by a simple power law function with index -1.34 +/- 0.03.

The event fluence (10-1000 keV) in this time interval is
(1.699 +/- 0.008)E-6 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-52.7 s in the 10-1000 keV band is 1.5 +/- 0.2 ph/s/cm^2. 

Due to the powering down of Fermi-GBM detectors because of SAA entry about 19 s 
after the trigger time (note T90), the T90 duration, peak fluxes and fluences 
are lower limits only.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"


GRB_name: GRB210402A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29764
SUBJECT: GRB 210402A: Swift/UVOT Upper Limits
DATE:    21/04/05 23:52:02 GMT
FROM:    Sam LaPorte at PSU  <sjl5346@psu.edu>

 GRB 210402A: Swift/UVOT Upper Limits

S. J. LaPorte (PSU) and K. L. Page (U Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210402A
73 s after the BAT trigger (Page et al., GCN Circ. 29743).
No optical afterglow consistent with the XRT position
(Evans et al. GCN Circ. 29750)
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           163          313          147         >20.8
u_FC               321          571          246         >20.3
white              163         1718          411         >21.4
v                  653         5581          229         >19.6
b                  578         1694          117         >20.2
u                  321         1669          304         >20.2
w1                1108         1644           78         >19.2
w2                1207         1227           19         >18.4

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.018 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210402A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29765
SUBJECT: GRB 210402A: MASTER prompt and follow up optical observation 
DATE:    21/04/06 08:33:46 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

K.Zhirkov, V. Lipunov, V.Kornilov, E.Gorbovskoy,P.Balanutsa,V.Vladimirov, A.Kuznetsov,
D. Vlasenko, N.Tiurina, I.Gorbunov, A.Chasovnikov, D.Zimnukhov, V.Senik, V.Topolev,
F.Balakin, D.Cheryasov (Lomonosov Moscow State University,SAI, Physics Department),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev (Irkutsk State University, API),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)

MASTER Global robotic net (MASTER-Net:http://observ.pereplet.ru 
Lipunov et al.,2010,Advances in Astronomy,2010,30L)
observed GRB 210402A (Swift trigger 1040123 Page et al. GCN 29743,
Evans et al. GCN 29750, Laha et al. 29761, Ttrigger=2021-04-02T22:03:17.22, 
also Fermi trigger #639093861   T_trigger(Fermi) = 22 04 17 Roberts et al. GCN 29763)
at MASTER-IAC, -Tavrida, -SAAO, -Kislovodsk, -OAFA, -Tunka (Lipunov et al. GCN 29741)
by MASTER-VWF cameras (two 24.3x16.2sq.deg.) with mlim=13
and by MASTER-II (two 4sq.deg.)  with mlims at MASTER cover map 
https://master.sai.msu.ru/site/master2/observ.php?id=1582249

We observed this field with the MASTER-VWFC of MASTER-IAC, covering the Swift/XRT position from 
2021-04-02 22:04:21 to 2021-04-02 22:07:17, i.e. during the prompt emission.
Frames were taken with the exposure time of 5s and with no filter .

Calibrated with NOMAD V-filter, we  marginally see optical source inside 
T90 at 2 images:
started at 2021-04-02 22:05:36(79 from Fermi trigger time) and
at 2021-04-02 22:05:46(89 from Fermi trigger)
with m_OT~11
at XRT position, but the pixel of this camera is 21".

Comparing to the GAIA EDR3, we see no optical counterpart down to the
magnitude of 10.5 at other images. It puts the upper limit on the flux of 
the prompt
optical emission at ~5e-10 erg cm^-2 s^-1. Considering that the x-ray flux
was ~1e-08 erg cm^-2 s^-1, we constrain the relation between optical flux
and x-ray flux at ~10^-2.


GRB_name: GRB210406A
Detection_method: INTEGRAL
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29767
SUBJECT: GRB 210406A: A long GRB detected by INTEGRAL
DATE:    21/04/06 17:58:19 GMT
FROM:    Sandro Mereghetti at IASF-Milano/INAF  <sandro.mereghetti@inaf.it>

S.Mereghetti (INAF, IASF-Milano), D.Gotz (CEA, Saclay),  C.Ferrigno,
E.Bozzo, V.Savchenko (ISDC, Versoix), L.Ducci (IAAT, Germany and ISDC,
Versoix) and J.Borkowski (CAMK, Torun) report:

a gamma ray burst lasting about 60 s has been detected by IBAS in the
 IBIS/ISGRI data at 17:11:22  UT of April 6, 2021.

The refined coordinates (J2000) are:
R.A.=  132.4589 deg
DEC.=  +76.5322  deg
with an uncertainty of 1.5 arcmin (90% c.l.).

Due to telemetry saturation, we can derive only lower limits on the fluence
and peak flux (20-200 keV).
These are  >1.2e-6 erg/cm2 and >1.6  ph/cm2/s (1-s integration  time),
 respectively.

A plot of the light curve will  be posted at
http://ibas.iasf-milano.inaf.it/IBAS_Results.html


GRB_name: GRB210406A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29768
SUBJECT: GRB 210406A: BOOTES-4/MET optical upper limit
DATE:    21/04/06 21:05:50 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

Y.-D. Hu, E. Fernandez-Garcia, A. J. Castro-Tirado, M.D. Caballero-Garcia, M. A. Castro Tirado (IAA-CSIC), C. Perez del Pulgar, A. Castellon, I. Carrasco (Univ. de Malaga), S. Guziy (Univ. of Nikolaev) and D. R. Xiong, Y. F. Fan, J. M. Bai, C. J. Wang, Y. X. Xin, X. H. Zhao (Yunnan Observatories of CAS) on behalf of a larger collaboration, report:

Following the detection of GRB 210406A by INTEGRAL (Mereghetti et al. GCNC 29767), the 0.6m BOOTES-4/MET robotic telescope at Lijiang Astronomical Observatory (China) automatically responded to the burst starting on Apr 6 at 17:13:27 UT  (~2 min after trigger). No new source is detected within the refined IBIS position (Mereghetti et al. GCNC 29767) down to 20.7 mag in the co-added image (878 s on the aggregate, clear filer). The non-detection is consistent with the limit reported by MASTER (Lipunov et al. GCNC 29766).

We thank the staff at Lijiang observatory for their excellent support.


GRB_name: GRB210406A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29769
SUBJECT: GRB 210406A: Konkoly Obs. optical upper limit
DATE:    21/04/07 00:42:09 GMT
FROM:    Jozsef Vinko at Konkoly Observator  <vinko@konkoly.hu>

J. Vinko (Konkoly/ELTE/U Szeged), R. Szakats, L. Kriskovics, A. Pal and K. Vida (Konkoly)
report on behalf of the "Transient Astrophysical Objects" project:

We observed the field of GRB 210406A (Mereghetti, GCN29767; Lipunov et al. GCN29766) with the 0.8m RC80 robotic telescope at Piszkesteto Mountain Station of Konkoly Observatory through SDSS r' and i' filters on 2021 Apr 06.86 UT
(MJD 59310.86, 3h 31.6m after the trigger). The total exposure time was 1800 s. The frames were tied
to PS1-photometry of local stellar sources. No optical counterpart for the GRB has been detected
above the 5-sigma upper limit of 21.9 AB-mag, which is consistent with other reports of non-detection
(Hu et al. GCN29768).


GRB_name: GRB210406A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29770
SUBJECT: GRB 210406A: Mondy optical upper limit
DATE:    21/04/07 10:25:25 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

N. Pankov (HSE), S. Belkin (IKI), A. Pozanenko (IKI), E. Klunko (ISTP) 
report  on behalf of GRB IKI FuN:

We observed the field of GRB 210406A (Mereghetti  et al., GCN 29767) 
with AZT-33IK telescope of Sayan observatory (Mondy) starting on 
2021-04-06 (UT) 17:54:58. We obtained 15 images in R-filter. We do not 
find new sources in a stacked image in comparison with Pan-STARRS PS1 or 
Legacy Survey which is consistent with observations (Lipunov et al., GCN 
29766; Hu et al., GCN 29768; Vinko  et al., GCN 29769). So we have no 
immediate OT candidate. More observation is necessary to investigate 
variability of field sources.
Preliminary photometry of the field in the stacked image is following

Date       UT start   t-T0       Filter Exp.   OT   Err.  UL(3sigma)
                      (mid, days)        (s)

2021-04-06 17:54:58   0.04069    R     15*120  n/d   n/d  22.9

The photometry is based on the nearby USNO-B1.0 stars
USNO-B1.0_id RA DEC R2
1665-0048950 132.414156 +76.555625 16.49
1664-0050141 132.551831 +76.468300 18.01


GRB_name: GRB210406A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29771
SUBJECT: GRB 210406A: Fermi GBM detection
DATE:    21/04/07 15:39:56 GMT
FROM:    Christian Malacaria at NASA-MSFC/USRA  <cmalacaria@usra.edu>

C. Malacaria (NASA-MSFC/USRA) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 17:11:30.57 UT on 06 April 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210406A (trigger 639421895 / 210406716),
which was also detected by the INTEGRAL/ISGRI (Mereghetti et al. 2021, GCN 29767).
The GBM on-ground location is consistent with the INTEGRAL position.

The angle from the Fermi LAT boresight at the GBM trigger time is 154 degrees.

The GBM light curve shows a long GRB with multiple spikes and
with a duration (T90) of about 17.4 s (50-300 keV).
The time-averaged spectrum from T0-2.0 s to T0+18.4 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.91 +/- 0.13 and
the cutoff energy, parameterized as Epeak, is 195.6 +/- 18.8 keV.

The event fluence (10-1000 keV) in this time interval is
(9.1 +/- 0.5)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+5.4 s in the 10-1000 keV band
is 4.6 +/- 0.6 ph/s/cm^2.


The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"


GRB_name: GRB210406A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29772
SUBJECT: Konus-Wind detection of GRB 210406A
DATE:    21/04/07 17:58:39 GMT
FROM:    Anna Ridnaia at Ioffe Institute  <ridnaia@mail.ioffe.ru>

A. Ridnaia, D. Frederiks, S. Golenetskii, A. Lysenko, D. Svinkin,
A. Tsvetkova,  M. Ulanov, and T. Cline, report:

The long GRB 210406A (INTEGRAL detection,
T0 = T0(IBIS/ISGRI)= 17:11:28 UT: Mereghetti, et al., GCN 29767;
Fermi/GBM detection: Malacaria & Meegan, GCN 29771)
was detected by Konus-Wind (KW) in the waiting mode.

A Bayesian block analysis of the KW waiting mode data in the 20-400 keV band
reveals a >10 sigma count rate increase over background in the interval
from ~T0-0.470 s to ~T0+73.130 s.

As observed by Konus-Wind, the burst had a fluence of
9.13(-1.16,+1.40)x10^-6 erg/cm2 and a 2.944-s peak flux,
measured in the interval starting from ~T0+5.418 s,
of 5.74(-0.84,+0.97)x10^-7 erg/cm2/s
(both in the 10 keV - 10 MeV energy range).

Modeling the K-W 3-channel time-integrated spectrum
(from ~T0-0.470 s to ~T0+73.130 s)
by a power law with exponential cutoff (CPL) model
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -1.04(-0.20,+0.35) and Ep = 176(-36,+54) keV.

The KW light curve of this burst is available at
http://www.ioffe.ru/LEA/GRBs/GRB210406A/

All the quoted errors are estimated at the 1 sigma confidence level.
All the presented results are preliminary.


GRB_name: GRB210406B
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29773
SUBJECT: GRB 210406B: Fermi GBM detection
DATE:    21/04/08 14:53:07 GMT
FROM:    Christian Malacaria at NASA-MSFC/USRA  <cmalacaria@usra.edu>

C. Malacaria (NASA-MSFC/USRA), O. Roberts (USRA) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 22:46:05.23 UT on 6 April 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210406B (trigger 639441970 / 210406949).

The on-ground calculated location, using the GBM trigger
data, is RA = 6.58, DEC = 19.58 (J2000 degrees,
equivalent to 00 h 26 m, 19 d 34 '), with an uncertainty of 1.5 degrees
(radius, 1-sigma containment, statistical only; there is additionally a 
systematic error which we have characterized as a mixture of two Gaussians,
one with a radius of 1.8 degrees (52% contribution) and one with a radius 
of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1] ).

The angle from the Fermi LAT boresight at the GBM trigger time is 83 degrees.

The GBM light curve consists of a long GRB with three
distinct peaks and with a duration (T90) of about 20 s (50-300 keV).
The spectrum shows a marked hard to soft evolution throughout the burst.
The time-averaged spectrum from T0+1.5 s to T0+20.9 s is
best fit by a Band function with Epeak = 53.4 +/- 0.7 keV,
alpha = -1.16 +/- 0.02, and beta = -3.06 +/- 0.09 .

The event fluence (10-1000 keV) in this time interval is
(2.423 +/- 0.027)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+10.7 s in the 10-1000 keV band
is 29.7 +/- 0.4 ph/s/cm^2.


The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"


GRB_name: GRB210406A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29774
SUBJECT: GRB 210406A: Swift ToO observations
DATE:    21/04/08 16:31:13 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a ToO observation of the INTEGRAL GRB 210406A. 
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021427

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the INTEGRAL event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a 
GCN Circular after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210406A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29775
SUBJECT: GRB 210406A: Mondy optical afterglow candidate
DATE:    21/04/08 20:53:54 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI), N. Pankov (HSE), A. Pozanenko (IKI), E. Klunko (ISTP) 
report  on behalf of GRB IKI FuN:

We observed the field of GRB 210406A (Mereghetti  et al., GCN 29767) 
with AZT-33IK telescope of Sayan observatory (Mondy) in second epoch 
starting on 2021-04-07 (UT) 16:54:14. The first epoch was obtained early 
(Pankov  et al., GCN 29770). We obtained 20 images in R-filter. In 
comparison of the sources we found one fading source in coordinates of 
(J2000) 08:49:49.09    76:33:20.2 with accuracy of 0.5 arcsec in each 
coordinate. The source is faded by 0.5mag between the two epochs. 
Preliminary photometry of the source in  stacked images is following

Date       UT start   t-T0       Filter Exp.   OT    Err.  UL(3sigma)
                     (mid, days)        (s)

2021-04-06 17:54:58   0.04069    R     15*120  21.90  0.14  22.9
2021-04-07 16:54:14   0.98811    R     20*120  22.41  0.14  23.2

The photometry is based on the nearby USNO-B1.0 stars
USNO-B1.0_id RA DEC R2
1665-0048950 132.414156 +76.555625 16.49
1664-0050141 132.551831 +76.468300 18.01

The source is not presented in Pan-STARRS PS1 but marginally  visible in 
Pan-STARRS (r-plate) and presented in Legacy Survey DR8.

We suggest the source as afterglow candidate of optical afterglow of GRB 
210406A.


GRB_name: GRB210410A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29777
SUBJECT: GRB 210410A: Fermi GBM Final Real-time Localization
DATE:    21/04/10 01:03:49 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 00:53:16 UT on 10 Apr 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210410A (trigger 639708801.519268 / 210410037).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 268.1, Dec = 47.2 (J2000 degrees, equivalent to J2000 17h 52m, 47d 12'), with a statistical uncertainty of 1.6 degrees.

The angle from the Fermi LAT boresight is 50.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210410037/quicklook/glg_skymap_all_bn210410037.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210410037/quicklook/glg_healpix_all_bn210410037.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210410037/quicklook/glg_lc_medres34_bn210410037.gif


GRB_name: GRB210410A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29778
SUBJECT: GRB 210410A: Swift XRT localization
DATE:    21/04/10 01:28:44 GMT
FROM:    Jamie A. Kennea at PSU/Swift-XRT  <kennea@swift.psu.edu>

A. Melandri (INAF-OAB), J. A. Kennea (PSU) and N. J. Klingler (PSU)
report on behalf of the Neil Gehrels Swift Observatory Team:

Swift BAT triggered on GRB 210410A, previously reported by Fermi/GBM (GCN #29777). 
Due to a telemetry drop-out, no prompt BAT data are available, however XRT has 
localized the source. 

Using promptly downlinked data we find an uncatalogued X-ray source
located at RA, Dec 269.75417, 45.36339 which is equivalent to:
   RA(J2000)  = 17h 59m 01.00s
   Dec(J2000) = +45d 21' 48.2"
with an uncertainty of 6.1 arcseconds (radius, 90% containment). This
position may be improved as more data are received; the latest position
is available at https://www.swift.ac.uk/sper. No spectrum from the
promptly downlinked event data is yet available to determine the column
density. 

Burst Advocate for this burst is A. Melandri (andrea.melandri AT brera.inaf.it). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB210410A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29779
SUBJECT: Fermi GRB 210410A: Global MASTER-Net observations report 
DATE:    21/04/10 01:30:12 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-SAAO robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 210410A ( Fermi GBM team, GCN 29777) errorbox  42 sec after notice time and 69 sec after trigger time at 2021-04-10 00:54:26 UT, with upper limit up to  16.8 mag. The observations began at zenith distance = 85 deg. The sun  altitude  is -50.6 deg. 

MASTER-Tavrida robotic telescope  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 210410A errorbox  112 sec after notice time and 139 sec after trigger time at 2021-04-10 00:55:36 UT, with upper limit up to  19.1 mag. The observations began at zenith distance = 15 deg. The sun  altitude  is -22.5 deg. 

The galactic latitude b = 29 deg., longitude l = 74 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1588428

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

      75 | 2021-04-10 00:54:26 |         MASTER-SAAO | (17h 48m 53.00s , +47d 14m 34.0s) |   C |    10 | 16.4 |        
     110 | 2021-04-10 00:54:56 |         MASTER-SAAO | (17h 48m 58.82s , +47d 13m 30.3s) |   C |    20 | 16.8 |        
     155 | 2021-04-10 00:55:36 |      MASTER-Tavrida | (17h 47m 38.38s , +48d 29m 25.0s) |   C |    30 | 18.4 |        
     209 | 2021-04-10 00:56:25 |      MASTER-Tavrida | (17h 47m 31.30s , +48d 28m 35.5s) |   C |    40 | 18.5 |        
     666 | 2021-04-10 01:03:22 |      MASTER-Tavrida | (17h 54m 11.52s , +47d 16m 38.2s) |   C |   120 | 19.1 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210410A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29780
SUBJECT: GRB210410A: Candidate optical afterglow by Ondrejov D50
DATE:    21/04/10 03:36:29 GMT
FROM:    Martin Jelinek at Astro.Inst-AVCR,Ondrejov  <martin.jelinek@asu.cas.cz>

M. Jelinek, J. Strobl, R. Hudec, C. Polasek (ASU CAS Ondrejov)
report:

We observed the position of the Fermi/GBM GRB 210410A (Fermi, GCNC 29777)
with the D50 robotic telescope of the Astronomical Institute Ondrejov, near
Prague, Czech Republic.  We performed a series of 120 s unfiltered
exposures starting 56 min after the trigger.

Within the Swift/XRT error box (Melandri et al. GCNC 29778) we detect a
fading object at (269.7542, 45.3629) (17:59:01.00 +45:21:46.6 J2000
+/-0.3").  The preliminary magnitude 103 min after the trigger was r'(AB) =
21.5 +/- 0.2 and the object seems to fade with alpha ~ 0.95 +/- 0.27.


GRB_name: GRB210410A
Detection_method: Fermi LAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29781
SUBJECT: GRB 210410A: Fermi-LAT detection
DATE:    21/04/10 08:25:22 GMT
FROM:    Makoto Arimoto at Tokyo Inst of Tech  <arimoto@hp.phys.titech.ac.jp>

M. Arimoto (Kanazawa Univ.), M. Ohno (Hiroshima Univ. & Eotvos Univ.),
F. Longo (University and INFN, Trieste) and M. Axelsson (KTH &
Stockholm Univ.) report on behalf of the Fermi-LAT team:

On April 10, 2021, Fermi-LAT detected high-energy emission from GRB
210410A, which was also detected by Fermi-GBM (trigger 639708801 /
210410037, Fermi GBM team, GCN 29777) and Swift/BAT&XRT (Kennea et al.
2021, GCN 29778).

The best LAT on-ground location is found to be
RA, Dec = 268.9, 45.2 (J2000)
with an error radius of 0.5 deg (90 % containment, statistical error
only). This position is consistent with the Swift/XRT localization.
This was 51 deg from the LAT boresight at the time of the GBM trigger:
T0 = 00:53:16.5 UT.

The data from the Fermi-LAT show a significant increase in the event
rate after the GBM trigger that is spatially and temporally correlated
with the GBM emission (2 degrees from the GBM location) with high
significance.

The photon flux above 100 MeV in the time interval 0-300s after the
GBM trigger is (4.0 +/- 0.7)e-05 ph/cm2/s, while the flux above 1 GeV
is (1.3 +/- 0.7)e-06 ph/cm2/s.

The estimated photon index above 100 MeV is -2.5 +/- 0.2.

The highest-energy photon is a 4.2 GeV event which is observed 30
seconds after the GBM trigger.

The Fermi-LAT point of contact for this burst is Masanori Ohno
(ohno@astro.hiroshima-u.ac.jp).

The Fermi-LAT is a pair conversion telescope designed to cover the
energy band from 20 MeV to greater than 300 GeV. It is the product of
an international collaboration between NASA and DOE in the U.S. and
many scientific institutions across France, Italy, Japan and Sweden.


GRB_name: GRB210410A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29782
SUBJECT: GRB 210410A: AGILE detection of a burst
DATE:    21/04/10 10:48:53 GMT
FROM:    Alessandro Ursi at INAF/IAPS  <alessandro.ursi@gmail.com>

A. Ursi (INAF/IAPS), F. Verrecchia, C. Pittori (SSDC, and INAF/OAR), M.
Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A. Argan, M. Cardillo, C.
Casentini, Y. Evangelista, G. Piano (INAF/IAPS), F. Lucarelli (SSDC, and
INAF/OAR), A. Bulgarelli, A. Di Piano, V. Fioretti, F. Fuschino, N.
Parmiggiani (INAF/OAS-Bologna), M. Marisaldi (INAF/OAS-Bologna, and Bergen
University), M. Pilia, A. Trois (INAF/OA-Cagliari), I. Donnarumma (ASI), F.
Longo (Univ. Trieste and INFN Trieste), A. Giuliani (INAF/IASF-Mi), report
on behalf of the AGILE Team:

The AGILE satellite detected the long GRB 210410A at T0 = 2021-04-10
00:53:16.64 +/- 0.01 s (UTC), reported by Fermi/GBM (GCN #29777), Swift/XRT
(GCN #29778), and Fermi/LAT (GCN #29781).

The burst is visible in the AGILE scientific ratemeters of the SuperAGILE
(SA; 20-60 keV), MiniCALorimeter (MCAL; 0.4-100 MeV), and AntiCoincidence
(AC; 50-200 keV) detectors. The event lasted ~15 s and released a total
number of 1050 counts in the SA detector (above a background rate of 60
Hz), 29400 counts in the MCAL detector (above a background rate of 1200
Hz), and 72250 counts in the AC detector (above a background rate of 3320
Hz). The AGILE ratemeter light curves can be found at
http://www.agilescienceapp.it/notices/GRB210410_AGILE_RM.png .

The event also triggered a partial high time resolution MCAL data
acquisition, whose light curve can be found at:
http://www.agilescienceapp.it/notices/072541_GRB_545100796.643050.png .

Additional analysis of AGILE data is in progress. Automatic MCAL GRB alert
Notices can be found at: https://gcn.gsfc.nasa.gov/agile_mcal.html.


GRB_name: GRB210409A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29783
SUBJECT: GRB 210409A: GECAM detection
DATE:    21/04/10 12:46:14 GMT
FROM:    Chao Zheng at IHEP  <zhengchao97@ihep.ac.cn>

C. Zheng, X. Y. Song, S. L. Xiong, X. Y. Zhao, D. Y. Guo, Y. Huang, S. Xiao,
C. Cai, Y. Zhao, J. C. Liu, Q. B. Yi, Y. Q. Zhang, W. C. Xue, Z. W. Guo,  
P. Wang, X. B. Li, W. X. Peng, R. Qiao, C. W. Wang,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, J. J. He,
B. Li, C. Li, C. Y. Li, J. H. Li, Q. X. Li, X. Q. Li, Y. G. Li, X. H. Liang,
J. Y. Liao, J. C. Liu, X. J. Liu, Y. Q. Liu, F. J. Lu, Q. Luo, X. Ma,
G. Ou,  D. L. Shi, J. Y. Shi, L. M. Song, G. X. Sun, X. L. Sun, Y. L. Tuo,
J. Z. Wang, X. Y. Wen, Y. B. Xu, Y. P. Xu, S. Yang, M. Yao, B. X. Zhang,
C. Y. Zhang, D. L. Zhang, Fan Zhang, Fei Zhang, H. M. Zhang, K. Zhang,
P. Zhang, S. N. Zhang, Z. Zhang, S. Y. Zhao, S. J. Zheng, X. Zhou (IHEP),
report on behalf of GECAM team:

During the commissioning phase, GECAM-B triggered a long burst,
GRB 210409A, at 2021-04-09T21:28:07.950 UTC (T0) from the ground search.
There is a weak precursor, by which the ground search found this burst,
~20 s before the main burst, which triggered GECAM-B in-flight as well.

According to the GECAM-B light curves in about 8 keV - 500 keV, 
this burst mainly consists of multiple pulses with duration of about 37 s.
Spectral evolution is clearly seen during the burst, and the emissions
in low energies last longer than that in high energies.

Although the in-flight calibration of energy response and localization
has not been finalized yet, GECAM-B localized this burst to the 
following position (J2000):
Ra: 70.9 deg 
Dec: -58.3 deg 
Err: 2.9 deg (1-sigma, statistical only) 

The current systematic error of location is estimated to be several degrees
which could be minimized by the ongoing calibration. 

The GECAM light curve could be found here: 
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/multiLCvsE_tn210409_212807.pdf

The GECAM preliminary location could be found here:  
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_skymap_bdm_71702907_V01.png

Please note that all GECAM results here are preliminary. The final analysis
will be published in journal papers or GECAM online catalog.

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in
Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time),
which was funded by the Chinese Academy of Sciences (CAS).


GRB_name: GRB210410A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29784
SUBJECT: GRB 210410A: RATIR Optical and NIR Observations
DATE:    21/04/10 13:41:41 GMT
FROM:    Nat Butler at Az State U  <natbutler@asu.edu>

Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William
H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier
Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora
Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), JesÃºs
GonzÃ¡lez (UNAM), Carlos RomÃ¡n-ZÃºÃ±iga (UNAM), Harvey Moseley (GSFC), John
Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report:

We observed the field of GRB 210410A (Fermi GBM team, et al., GCN 29777)
with the Reionization and Transients Infrared Camera (RATIR) on the 1.5m
Harold Johnson Telescope at the Observatorio AstronÃ³mico Nacional on Sierra
San Pedro MÃ¡rtir from 2021/04 10.30 to 2021/04 10.51 UTC (6.26 to 11.25
hours after the BAT trigger), obtaining a total of 2.16 hours exposure in
the r and i bands and 0.87 hours exposure in the Z, Y, J, and H bands.

We detect one source within the Swift-XRT error circle (Melandri, et al.,
GCN 29778).  In comparison with the USNO-B1 and 2MASS catalogs, we find
these magnitudes (in the AB system and not corrected for Galactic
extinction in the direction of the GRB):

  r     = 23.79 +/- 0.30
  i     = 22.49 +/- 0.14
  Z     = 22.07 +/- 0.27
  Y     = 21.14 +/- 0.18
  J     = 20.24 +/- 0.11
  H     = 20.17 +/- 0.15

The source is located at RA, Dec = 17:59:1.00, +45:21:44.6 (J2000,
+/-0.5"), which is 2 arcsec away from the candidate optical afterglow
position reported by Jelinek et al. (GCN 29780).  It is possible that an
astrometric cross-comparison could reveal our sources to be the same, in
which case the optical afterglow continues to fade strongly.  It is also
possible that we are detecting the GRB host galaxy.  A photo-z analysis
suggests the redshift is z<3.6 (90% confidence).

We thank the staff of the Observatorio AstronÃ³mico Nacional in San Pedro
MÃ¡rtir.


GRB_name: GRB210406A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29785
SUBJECT: GRB 210406A: Swift-XRT observations
DATE:    21/04/10 14:34:44 GMT
FROM:    Paolo D'Avanzo at INAF - OAB  <paolo.davanzo@inaf.it>

V. D'Elia (SSDC & INAF-OAR), A. D'Ai (INAF-IASFPA), B. Sbarufatti
(PSU), D.N. Burrows (PSU), J. D. Gropp (PSU), K.L. Page (U. Leicester),
A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAB) and P.A. Evans
(U. Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the INTEGRAL-detected
burst GRB 210406A (Mereghetti et al. GCN Circ. 29767), collecting 5.1
ks of Photon Counting (PC) mode data between T0+169.5 and T0+244.5 ks. 


One uncatalogued X-ray source has been detected consistent with being
within 148 arcsec of the INTEGRAL position, it is below the RASS limit
and shows no definitive signs of fading. Therefore, at the present time
we cannot confirm this as the afterglow. Details of this source are
given below:

Source 3:
  RA (J2000):  132.4988  =  08:49:59.72
  Dec (J2000): +76.5289  =  +76:31:44.0
  Error: 6.4 arcsec (radius, 90% conf.)
  Count-rate: (1.28 [+0.75, -0.56])e-3 ct s^-1  
  Distance: 35 arcsec from INTEGRAL position.
  Flux: (1.46 [+0.86, -0.64])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)


An uncatalogued source was also detected, however this was too far from
the GRB position to be the afterglow.

No X-ray source is detected at the position of the optical afterglow
candidate reported by Belkin et al. (GCN Circ. 29775) down to a 3sigma
upper limit of 1.4e-3 ct s^-1.

The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
https://www.swift.ac.uk/ToO_GRBs/00021427.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210410A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29786
SUBJECT: GRB210410A: Joint inspection of RATIR and D50 data
DATE:    21/04/10 15:36:33 GMT
FROM:    Martin Jelinek at Astro.Inst-AVCR,Ondrejov  <martin.jelinek@asu.cas.cz>

Nat Butler (ASU) and Martin Jelinek (ASU AV CR Ondrejov) report:

We performed a joint inspection of the D50 (Jelinek et al., GCNC29780) and
RATIR (Butler et al.,  GCNC29784) images and agreed that the object
reported in both circulars is identical. Joint photometric fit of the data
provides a decay rate of 1.18 Â± 0.24 (chisq=1.68). Seeing this, we conclude
that this object is indeed the optical afterglow of GRB 210410A  (cf. Fermi
team, GCN 29777, Melandri et al., GCN 29778, Arimoto at al., GCN
29781, Ursi et al., GCNC 29782).

The preliminary coordinates reported by the D50 team are flawed and the
RATIR value, i.e. RA, Dec = 17:59:1.00, +45:21:44.6 (J2000, +/-0.5") should
be used.


GRB_name: GRB210410A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29787
SUBJECT: GRB 210410A: Swift/UVOT Upper Limits
DATE:    21/04/10 21:16:09 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

Paul Kuin (MSSL/UCL) and A. Melandri(INAF-OAB) report on behalf
of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210410A
(trigger 01042113; previously reported by Fermi/GBM in GCN #29777)
1113 s after the Fermi trigger at 2021-04-10 00:53:16 UT.
No optical afterglow consistent with the XRT position (Melandri et
al. GCN Circ. 29778) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)       mag 3-sigma UL

v                 1129         1149           19         >17.0
b                 5021         5109           85         >19.7
u                 4817         5014          197         >19.9
w1                4610         4809          197         >19.3
m2                4403         4602          197         >19.4
w2                1113         1125           12         >17.0

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.05 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210410A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29788
SUBJECT: GRB 210410A: Fermi GBM detection
DATE:    21/04/11 01:42:52 GMT
FROM:    Joshua Wood at MSFC/Fermi-GBM  <joshua.r.wood@nasa.gov>

J. Wood (NASA/MSFC) and C.Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 00:53:16.52 UT on 10 April 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210410A (trigger 639708801 / 210410037).
which was also detected by the Swift/XRT (A. Melandri et al. 2021, GCN 29778),
the Fermi/LAT (M. Arimoto et al. 2021, GCN 29781),
and AGILE (A. Ursi et al. 2021, GCN 29782).

The Fermi GBM Final Real-time Localization (GCN 29777) is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 51.0 degrees.

The GBM light curve consists of a single peak
with a duration (T90) of about 48 s (50-300 keV).
The time-averaged spectrum from T0-0 s to T0+50 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.70 +/- 0.02 and
the cutoff energy, parameterized as Epeak, is 1300 +/- 100 keV

The event fluence (10-1000 keV) in this time interval is
(4.5 +/- 0.5)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0 s in the 10-1000 keV band
is 12.6 +/- 0.3 ph/s/cm^2.

A Band function fits the spectrum equally well 
with Epeak = 1300 +/- 100 keV, alpha = -0.70 +/- 0.03 and beta = 4.0 +/- 1.6.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"


GRB_name: GRB210411A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29789
SUBJECT: GRB 210411A: Fermi GBM Final Real-time Localization
DATE:    21/04/11 03:41:20 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 03:30:56 UT on 11 Apr 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210411A (trigger 639804661.435174 / 210411146).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 259.4, Dec = -27.4 (J2000 degrees, equivalent to J2000 17h 17m, -27d 23'), with a statistical uncertainty of 3.0 degrees.

The angle from the Fermi LAT boresight is 90.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210411146/quicklook/glg_skymap_all_bn210411146.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210411146/quicklook/glg_healpix_all_bn210411146.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210411146/quicklook/glg_lc_medres34_bn210411146.gif


GRB_name: GRB210410A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29790
SUBJECT: GRB 210410A: Swift-XRT refined Analysis
DATE:    21/04/11 04:35:55 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

A. D'Ai (INAF-IASFPA), D.N. Burrows (PSU), J. D. Gropp (PSU), J.A.
Kennea (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester),
J.P. Osborne (U. Leicester), A. Melandri (INAF-OAB), T. Sbarrato
(INAF-OAB) and report on behalf of the Swift-XRT team: report on
behalf of the Swift-XRT team:

We have analysed 4.4 ks of XRT data for GRB 210410A, from 61 s to 52.6
ks after the  BAT trigger. The data comprise 115 s in Windowed Timing
(WT) mode (the first 8 s were taken while Swift was slewing) with the
remainder in Photon Counting (PC) mode. Using 702 s of PC mode data and
1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT
alignment and matching UVOT field sources to the USNO-B1 catalogue):
RA, Dec = 269.75437, +45.36192 which is equivalent to:

RA (J2000): 17h 59m 01.05s
Dec(J2000): +45d 21' 42.9"

with an uncertainty of 2.4 arcsec (radius, 90% confidence).

The late-time light curve (from T0+4.3 ks) can be modelled with a
power-law decay with a decay index of alpha=1.5 (+0.5, -0.4).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.33 (+/-0.11). The
best-fitting absorption column is  1.4 (+0.5, -0.4) x 10^21 cm^-2, in
excess of the Galactic value of 4.0 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.47 (+0.18, -0.16)
and a best-fitting absorption column of 7.2 (+6.0, -3.2) x 10^20 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 4.5 x 10^-11 (4.9 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      7.2 (+6.0, -3.2) x 10^20 cm^-2
Galactic foreground: 4.0 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.47 (+0.18, -0.16)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01042113.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210411A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29791
SUBJECT: Fermi GRB 210411A: Global MASTER-Net observations report 
DATE:    21/04/11 07:26:49 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-OAFA robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 210411A ( Fermi GBM team, GCN 29789) errorbox  471 sec after notice time and 547 sec after trigger time at 2021-04-11 03:40:04 UT, with upper limit up to  17.7 mag. The observations began at zenith distance = 65 deg. The sun  altitude  is -63.8 deg. 

MASTER-IAC robotic telescope  located in Spain (IAC Teide Observatory) started inspect of the Fermi GRB 210411A errorbox  519 sec after notice time and 595 sec after trigger time at 2021-04-11 03:40:52 UT, with upper limit up to  18.4 mag. The observations began at zenith distance = 59 deg. The sun  altitude  is -37.5 deg. 

The galactic latitude b =  5 deg., longitude l = 358 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1589139

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

     578 | 2021-04-11 03:40:04 |         MASTER-OAFA | (17h 23m 57.03s , -26d 40m 24.3s) |   C |    60 | 16.8 |        
     656 | 2021-04-11 03:40:52 |          MASTER-IAC | (17h 16m 27.13s , -27d 21m 57.1s) |  P| |   120 | 17.5 |        
     656 | 2021-04-11 03:40:52 |          MASTER-IAC | (17h 15m 35.27s , -27d 16m 25.1s) |  P- |   120 | 17.1 |        
     687 | 2021-04-11 03:41:23 |         MASTER-OAFA | (17h 15m 40.62s , -28d 03m 11.8s) |   C |   120 | 16.8 |        
     811 | 2021-04-11 03:43:12 |          MASTER-IAC | (17h 16m 20.96s , -27d 22m 43.5s) |  P| |   150 | 17.7 |        
     811 | 2021-04-11 03:43:12 |          MASTER-IAC | (17h 15m 29.22s , -27d 17m 12.1s) |  P- |   150 | 17.3 |        
     842 | 2021-04-11 03:43:43 |         MASTER-OAFA | (17h 15m 36.38s , -28d 04m 04.6s) |   C |   150 | 16.8 |        
     996 | 2021-04-11 03:46:02 |          MASTER-IAC | (17h 16m 19.84s , -27d 21m 46.4s) |  P| |   180 | 17.8 |        
     996 | 2021-04-11 03:46:02 |          MASTER-IAC | (17h 15m 28.23s , -27d 16m 14.6s) |  P- |   180 | 17.4 |        
    1026 | 2021-04-11 03:46:32 |         MASTER-OAFA | (17h 15m 35.02s , -28d 03m 04.0s) |   C |   180 | 16.8 |        
    1196 | 2021-04-11 03:49:22 |          MASTER-IAC | (17h 16m 27.03s , -27d 22m 48.9s) |  P| |   180 | 17.9 |        
    1196 | 2021-04-11 03:49:22 |          MASTER-IAC | (17h 15m 35.46s , -27d 17m 16.5s) |  P- |   180 | 17.4 |        
    1226 | 2021-04-11 03:49:52 |         MASTER-OAFA | (17h 15m 41.93s , -28d 04m 03.5s) |   C |   180 | 16.8 |        
    1336 | 2021-04-11 03:52:42 |          MASTER-IAC | (16h 57m 35.03s , -25d 59m 03.8s) |   C |    60 | 18.1 |        
    1743 | 2021-04-11 03:59:29 |         MASTER-OAFA | (17h 07m 01.29s , -28d 38m 16.1s) |   C |    60 | 15.9 |        
    1902 | 2021-04-11 04:02:08 |         MASTER-OAFA | (17h 08m 31.62s , -30d 40m 19.6s) |   C |    60 | 16.4 |        
    1982 | 2021-04-11 04:03:28 |         MASTER-OAFA | (17h 25m 05.73s , -28d 38m 57.0s) |   C |    60 | 16.7 |        
    2061 | 2021-04-11 04:04:47 |         MASTER-OAFA | (17h 07m 39.23s , -24d 38m 32.1s) |   C |    60 | 17.1 |        
    2141 | 2021-04-11 04:06:06 |         MASTER-OAFA | (17h 26m 59.74s , -30d 38m 52.5s) |   C |    60 | 17.1 |        
    2220 | 2021-04-11 04:07:26 |         MASTER-OAFA | (17h 25m 04.94s , -24d 40m 44.2s) |   C |    60 | 17.1 |        
    2776 | 2021-04-11 04:16:42 |         MASTER-OAFA | (17h 24m 30.83s , -26d 40m 18.9s) |   C |    60 | 17.0 |        
    2856 | 2021-04-11 04:18:02 |         MASTER-OAFA | (17h 33m 22.43s , -26d 39m 19.0s) |   C |    60 | 16.7 |        
    3094 | 2021-04-11 04:22:00 |         MASTER-OAFA | (17h 06m 55.34s , -28d 39m 13.6s) |   C |    60 | 16.6 |        
    3174 | 2021-04-11 04:23:20 |         MASTER-OAFA | (17h 15m 59.88s , -28d 38m 29.9s) |   C |    60 | 16.5 |        
    3253 | 2021-04-11 04:24:39 |         MASTER-OAFA | (17h 06m 42.93s , -26d 39m 11.2s) |   C |    60 | 17.0 |        
    3333 | 2021-04-11 04:25:59 |         MASTER-OAFA | (17h 15m 32.72s , -26d 40m 27.0s) |   C |    60 | 17.3 |        
    3413 | 2021-04-11 04:27:19 |         MASTER-OAFA | (17h 08m 38.69s , -30d 40m 14.5s) |   C |    60 | 16.5 |        
    3492 | 2021-04-11 04:28:38 |         MASTER-OAFA | (17h 17m 49.03s , -30d 38m 47.3s) |   C |    60 | 16.9 |        
    3572 | 2021-04-11 04:29:58 |         MASTER-OAFA | (17h 25m 05.83s , -28d 40m 40.6s) |   C |    60 | 16.4 |        
    3652 | 2021-04-11 04:31:17 |         MASTER-OAFA | (17h 34m 13.32s , -28d 39m 33.2s) |   C |    60 | 17.1 |        
    3731 | 2021-04-11 04:32:37 |         MASTER-OAFA | (17h 07m 34.30s , -24d 39m 09.5s) |   C |    60 | 17.2 |        
    3810 | 2021-04-11 04:33:56 |         MASTER-OAFA | (17h 16m 19.44s , -24d 38m 25.5s) |   C |    60 | 17.5 |        
    3890 | 2021-04-11 04:35:16 |         MASTER-OAFA | (17h 27m 06.93s , -30d 39m 52.1s) |   C |    60 | 17.2 |        
    4049 | 2021-04-11 04:37:55 |         MASTER-OAFA | (17h 25m 10.73s , -24d 40m 23.0s) |   C |    60 | 17.0 |        
    4447 | 2021-04-11 04:44:33 |         MASTER-OAFA | (16h 57m 52.45s , -28d 37m 54.7s) |   C |    60 | 16.8 |        
    4561 | 2021-04-11 04:45:27 |          MASTER-IAC | (17h 16m 28.39s , -27d 23m 28.5s) |   C |   180 | 18.0 |        
    4561 | 2021-04-11 04:45:27 |          MASTER-IAC | (17h 15m 35.51s , -27d 17m 35.6s) |   C |   180 | 17.8 |        
    4761 | 2021-04-11 04:48:47 |          MASTER-IAC | (17h 16m 26.15s , -27d 21m 56.5s) |   C |   180 | 18.2 |        
    4761 | 2021-04-11 04:48:47 |          MASTER-IAC | (17h 15m 33.23s , -27d 16m 03.3s) |   C |   180 | 18.0 |        
    4848 | 2021-04-11 04:51:14 |         MASTER-OAFA | (17h 24m 28.58s , -26d 40m 23.5s) |   C |    60 | 17.2 |        
    4961 | 2021-04-11 04:52:07 |          MASTER-IAC | (17h 14m 50.98s , -24d 59m 25.1s) |   C |   180 | 18.4 |        
    4961 | 2021-04-11 04:52:07 |          MASTER-IAC | (17h 13m 59.01s , -24d 53m 30.8s) |   C |   180 | 18.1 |        
    4927 | 2021-04-11 04:52:33 |         MASTER-OAFA | (17h 33m 24.93s , -26d 39m 14.1s) |   C |    60 | 17.7 |        
    5086 | 2021-04-11 04:55:12 |         MASTER-OAFA | (17h 06m 56.82s , -28d 38m 10.1s) |   C |    60 | 16.6 |        
    5162 | 2021-04-11 04:55:28 |          MASTER-IAC | (17h 14m 54.31s , -24d 57m 58.9s) |   C |   180 | 18.3 |        
    5162 | 2021-04-11 04:55:28 |          MASTER-IAC | (17h 14m 02.39s , -24d 52m 04.4s) |   C |   180 | 18.1 |        
    5167 | 2021-04-11 04:56:33 |         MASTER-OAFA | (17h 16m 07.09s , -28d 39m 27.1s) |   C |    60 | 16.8 |        
    5246 | 2021-04-11 04:57:52 |         MASTER-OAFA | (17h 06m 37.55s , -26d 40m 07.6s) |   C |    60 | 17.0 |        
    5362 | 2021-04-11 04:58:48 |          MASTER-IAC | (17h 14m 48.25s , -24d 58m 33.7s) |   C |   180 | 18.3 |        
    5362 | 2021-04-11 04:58:48 |          MASTER-IAC | (17h 13m 56.34s , -24d 52m 39.2s) |   C |   180 | 18.0 |        
    5326 | 2021-04-11 04:59:12 |         MASTER-OAFA | (17h 15m 37.02s , -26d 39m 58.4s) |   C |    60 | 17.4 |        
    5405 | 2021-04-11 05:00:31 |         MASTER-OAFA | (17h 08m 35.24s , -30d 38m 18.2s) |   C |    60 | 16.6 |        
    5489 | 2021-04-11 05:01:55 |         MASTER-OAFA | (17h 17m 49.41s , -30d 40m 16.0s) |   C |    60 | 16.9 |        
    5570 | 2021-04-11 05:03:16 |         MASTER-OAFA | (17h 25m 09.81s , -28d 38m 53.8s) |   C |    60 | 16.7 |        
    5650 | 2021-04-11 05:04:36 |         MASTER-OAFA | (17h 34m 06.46s , -28d 40m 01.2s) |   C |    60 | 17.1 |        
    6166 | 2021-04-11 05:12:12 |          MASTER-IAC | (17h 06m 52.58s , -26d 29m 21.6s) |   C |   180 | 17.7 |        
    6166 | 2021-04-11 05:12:12 |          MASTER-IAC | (17h 05m 58.31s , -26d 23m 16.7s) |   C |   180 | 17.6 |        
    6365 | 2021-04-11 05:15:31 |          MASTER-IAC | (17h 06m 50.56s , -26d 27m 49.5s) |   C |   180 | 17.7 |        
    6365 | 2021-04-11 05:15:31 |          MASTER-IAC | (17h 05m 56.28s , -26d 21m 43.6s) |   C |   180 | 17.6 |        
    6565 | 2021-04-11 05:18:51 |          MASTER-IAC | (17h 14m 50.19s , -29d 29m 31.1s) |   C |   180 | 17.6 |        
    6565 | 2021-04-11 05:18:51 |          MASTER-IAC | (17h 13m 54.90s , -29d 23m 26.7s) |   C |   180 | 17.5 |        
    6765 | 2021-04-11 05:22:11 |          MASTER-IAC | (17h 14m 52.37s , -29d 28m 07.3s) |   C |   180 | 17.7 |        
    6765 | 2021-04-11 05:22:11 |          MASTER-IAC | (17h 13m 57.12s , -29d 22m 02.0s) |   C |   180 | 17.6 |        
    6965 | 2021-04-11 05:25:31 |          MASTER-IAC | (17h 14m 47.25s , -25d 58m 47.6s) |   C |   180 | 18.0 |        
    6965 | 2021-04-11 05:25:31 |          MASTER-IAC | (17h 13m 53.52s , -25d 52m 41.3s) |   C |   180 | 17.8 |        
    7165 | 2021-04-11 05:28:51 |          MASTER-IAC | (17h 14m 48.35s , -25d 57m 48.6s) |   C |   180 | 18.2 |        
    7165 | 2021-04-11 05:28:51 |          MASTER-IAC | (17h 13m 54.58s , -25d 51m 41.5s) |   C |   180 | 18.0 |        
    7365 | 2021-04-11 05:32:11 |          MASTER-IAC | (17h 14m 53.08s , -25d 58m 50.2s) |   C |   180 | 18.2 |        
    7365 | 2021-04-11 05:32:11 |          MASTER-IAC | (17h 13m 59.18s , -25d 52m 42.8s) |   C |   180 | 18.0 |        
    7565 | 2021-04-11 05:35:31 |          MASTER-IAC | (17h 14m 47.34s , -25d 59m 51.5s) |   C |   180 | 18.2 |        
    7565 | 2021-04-11 05:35:31 |          MASTER-IAC | (17h 13m 53.40s , -25d 53m 44.2s) |   C |   180 | 18.0 |        
    7765 | 2021-04-11 05:38:51 |          MASTER-IAC | (17h 30m 53.67s , -28d 59m 51.5s) |   C |   180 | 17.6 |        
    7765 | 2021-04-11 05:38:51 |          MASTER-IAC | (17h 29m 58.53s , -28d 53m 45.8s) |   C |   180 | 17.5 |        
    7965 | 2021-04-11 05:42:11 |          MASTER-IAC | (17h 30m 50.06s , -28d 58m 34.3s) |   C |   180 | 17.6 |        
    7965 | 2021-04-11 05:42:11 |          MASTER-IAC | (17h 29m 54.98s , -28d 52m 28.7s) |   C |   180 | 17.5 |        
    8166 | 2021-04-11 05:45:31 |          MASTER-IAC | (17h 30m 50.90s , -24d 29m 52.0s) |   C |   180 | 18.3 |        
    8166 | 2021-04-11 05:45:31 |          MASTER-IAC | (17h 29m 57.63s , -24d 23m 44.8s) |   C |   180 | 18.0 |        
    8365 | 2021-04-11 05:48:51 |          MASTER-IAC | (17h 30m 54.12s , -24d 28m 39.8s) |   C |   180 | 18.2 |        
    8365 | 2021-04-11 05:48:51 |          MASTER-IAC | (17h 30m 00.85s , -24d 22m 31.9s) |   C |   180 | 17.9 |        
    8566 | 2021-04-11 05:52:12 |          MASTER-IAC | (17h 18m 47.18s , -30d 59m 07.8s) |   C |   180 | 17.5 |        
    8566 | 2021-04-11 05:52:12 |          MASTER-IAC | (17h 17m 51.23s , -30d 53m 02.9s) |   C |   180 | 17.3 |        
    8766 | 2021-04-11 05:55:32 |          MASTER-IAC | (17h 18m 47.47s , -30d 58m 10.4s) |   C |   180 | 17.4 |        
    8766 | 2021-04-11 05:55:32 |          MASTER-IAC | (17h 17m 51.55s , -30d 52m 04.7s) |   C |   180 | 17.1 |        
    8966 | 2021-04-11 05:58:52 |          MASTER-IAC | (17h 18m 53.62s , -22d 29m 04.5s) |   C |   180 | 17.3 |        
    8966 | 2021-04-11 05:58:52 |          MASTER-IAC | (17h 18m 01.13s , -22d 22m 55.5s) |   C |   180 | 17.1 |        
    9166 | 2021-04-11 06:02:12 |          MASTER-IAC | (17h 18m 47.44s , -22d 30m 05.5s) |   C |   180 | 17.2 |        
    9166 | 2021-04-11 06:02:12 |          MASTER-IAC | (17h 17m 54.95s , -22d 23m 56.9s) |   C |   180 | 17.0 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210411B
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29792
SUBJECT: GRB 210411B: Fermi GBM Final Real-time Localization
DATE:    21/04/11 13:43:07 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 13:32:44 UT on 11 Apr 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210411B (trigger 639840769.632692 / 210411564).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 115.7, Dec = -74.8 (J2000 degrees, equivalent to J2000 07h 42m, -74d 47'), with a statistical uncertainty of 4.5 degrees.

The angle from the Fermi LAT boresight is 60.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210411564/quicklook/glg_skymap_all_bn210411564.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210411564/quicklook/glg_healpix_all_bn210411564.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210411564/quicklook/glg_lc_medres34_bn210411564.gif


GRB_name: GRB210410A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29793
SUBJECT: GRB 210410A: Swift-BAT refined analysis
DATE:    21/04/11 14:53:46 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), C. B. Markwardt (GSFC),
A. Melandri (INAF-OAB), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-239 to T+963 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 210410A (trigger #1042113)
(Melandri et al., GCN Circ. 29778).  The BAT ground-calculated position is
RA, Dec = 269.741, 45.359 deg which is
   RA(J2000)  =  17h 58m 57.8s
   Dec(J2000) = +45d 21' 31.9"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 55%.

The mask-weighted light curve shows a FRED pulse that starts at ~T0, peaks
at ~T0, peaks at ~T+2 s, and ends at ~T+100 s. T90 (15-350 keV)
is 52.88 +- 4.15 sec (estimated error including systematics).

The time-averaged spectrum from T-0.00 to T+66.06 sec is best fit by a
simple
power-law model.  The power law index of the time-averaged spectrum is
1.04 +- 0.06.  The fluence in the 15-150 keV band is 5.6 +- 0.2 x 10^-6
erg/cm2.
The 1-sec peak photon flux measured from T+1.74 sec in the 15-150 keV band
is 4.0 +- 0.3 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1042113/BA/


GRB_name: GRB210411C
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29794
SUBJECT: GRB 210411C: Swift detection of a burst with an optical counterpart
DATE:    21/04/11 15:16:46 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

T. Sbarrato (INAF-OAB), M. G. Bernardini (INAF-OAB),
P. D'Avanzo (INAF-OAB), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB),
K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of
the Neil Gehrels Swift Observatory Team:

At 15:05:51 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210411C (trigger=1042398).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 296.559, -39.373 which is 
   RA(J2000) = 19h 46m 14s
   Dec(J2000) = -39d 22' 21"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multi-peaked
structure with a duration of about 20 sec.  The peak count rate
was ~5500 counts/sec (15-350 keV), at ~4 sec after the trigger. 

The XRT began observing the field at 15:06:54.6 UT, 63.1 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 296.60899, -39.39786 which is
equivalent to:
   RA(J2000)  = 19h 46m 26.16s
   Dec(J2000) = -39d 23' 52.3"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 165 arcseconds from the BAT onboard position, within the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
https://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (8.10 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.2
(+2.66/-2.35) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of nominal 150.000 seconds with the White
filter starting 66 seconds after the BAT trigger. There is a candidate
afterglow in the list of sources generated on-board at
  RA(J2000)  = 19:46:26.83 = 296.61178
  DEC(J2000) = -39:23:51.9  = -39.39774
with a 90%-confidence error radius of about 1.10 arc sec. This position is 7.0
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.99. No correction has been made for the expected extinction corresponding to
E(B-V) of 0.080. 

Burst Advocate for this burst is T. Sbarrato (tullia.sbarrato AT inaf.it). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB210411D
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29795
SUBJECT: GRB 210411D: Fermi GBM Final Real-time Localization
DATE:    21/04/11 16:41:35 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 16:31:10 UT on 11 Apr 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210411D (trigger 639851475.876502 / 210411688).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 358.5, Dec = 24.3 (J2000 degrees, equivalent to J2000 23h 53m, 24d 18'), with a statistical uncertainty of 3.6 degrees.

The angle from the Fermi LAT boresight is 55.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210411688/quicklook/glg_skymap_all_bn210411688.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210411688/quicklook/glg_healpix_all_bn210411688.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210411688/quicklook/glg_lc_medres34_bn210411688.gif


GRB_name: GRB210411D
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29796
SUBJECT: GRB 210411D: BALROG localization (Fermi Trigger 639851475 / GRB 210411688)
DATE:    21/04/11 16:59:18 GMT
FROM:    Jochen Greiner at MPI  <jcg@mpe.mpg.de>

F. Kunzweiler, B. Biltzinger, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
 at 16:31:10 on 11 Apr. 2021 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).

The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 340.7+/-4.8 deg
Decl.(2000.0) = 36.6+/-3.2 deg
We estimate an additional systematic error of 2 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210411688/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210411688/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210411688/json

                        


GRB_name: GRB210410A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29797
SUBJECT: Konus-Wind detection of GRB 210410A
DATE:    21/04/11 18:02:54 GMT
FROM:    Anna Ridnaia at Ioffe Institute  <ridnaia@mail.ioffe.ru>

A. Ridnaia, D. Frederiks, S. Golenetskii, A. Lysenko, D. Svinkin,
A. Tsvetkova,  M. Ulanov, and T. Cline, report:

The long-duration GRB 210410A
(Fermi-GBM detection: Fermi GBM team, GCN 29777,
Wood and Meegan, GCN 29788;
Fermi-LAT detection: Arimoto et al., GCN 29781;
AGILE detection: Ursi et al., GCN 29782;
Swift-BAT observation: Lien et al., GCN 29793)
triggered Konus-Wind at T0=3196.651 s UT (00:53:16.651).

The burst light curve starts at ~T0 with a narrow (~128 ms) pulse
followed by a gradually decaying emission until ~T0+85s.
The emission is seen up to ~10 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210410_T03196/

As observed by Konus-Wind, the burst
had a fluence of 7.29(-0.44,+0.47)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+0.002 s,
of 2.95(-0.69,+0.76)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+47.104 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.74(-0.07,+0.08)
and Ep = 1081(-126,+150) keV (chi2 = 72/98 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.7
(chi2 = 72/97 dof).

The spectrum of the initial pulse
(measured from T0 to T0+0.128 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model
with  alpha = 0.11(-0.29,+0.38)
and Ep = 1210(-250,+326) keV (chi2 = 38/32 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -1.9
(chi2 = 36/31 dof).

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.


GRB_name: GRB210410A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29798
SUBJECT: GRB 210410A: AGILE/MCAL analysis
DATE:    21/04/11 19:51:25 GMT
FROM:    Alessandro Ursi at INAF/IAPS  <alessandro.ursi@gmail.com>

A. Ursi (INAF/IAPS), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), F.
Verrecchia, C. Pittori (SSDC, and INAF/OAR), A. Argan, M. Cardillo, C.
Casentini, Y. Evangelista, G. Piano (INAF/IAPS), F. Lucarelli (SSDC, and
INAF/OAR), A. Bulgarelli, A. Di Piano, V. Fioretti, F. Fuschino, N.
Parmiggiani (INAF/OAS-Bologna), M. Marisaldi (INAF/OAS-Bologna, and Bergen
University), M. Pilia, A. Trois (INAF/OA-Cagliari), I. Donnarumma (ASI), F.
Longo (Univ. Trieste and INFN Trieste), A. Giuliani (INAF/IASF-Mi), report
on behalf of the AGILE Team:

We carried out further analysis of the AGILE/MCAL data of GRB 210410A (GCNs
#29777, #29778, #29779, #29780, #29781, #29782, #29786, #29787, #29788,
#29790, #29793, #29797).

The first 4 s of the burst released 5700 counts in the detector, above a
background rate of 560 Hz.
The spectral analysis shows a clear component up to 100 MeV.

The time-integrated spectrum of the first ~4 s of the burst can be fitted
in the energy range 0.4-100 MeV with a CPL model with alpha = -0.6
-0.25/+0.14 and cutoff energy Ec = 500 keV, plus an extra PL component with
ph.ind. -1.31 -0.04/+0.04. The fit results in a reduced chi-squared of 1.48
(81 d.o.f.) and a fluence of 1.3e-04 ergs/cm^2 (90% confidence level), in
the same energy range.

We divided the data acquisition into three time intervals: interval a
[T0-0.16s - T0+0.70s], interval b [T0+0.70s - T0+2.85s], and interval c
[T0+2.85s - T0+4.00s]. The spectral analysis in the energy range 0.4-100
MeV shows an evolution of the PL high-energy spectral component, evolving
from alpha = -1.91 to alpha = -0.92. Details are reported below:

  |  model |         CPL alpha |      Ec |        PL ph.ind. | redX^2 (dof)
a | CPL+PL | -0.57 -1.46/+3.84 | 438 keV | -1.91 -0.96/+0.78 |    0.97 (81)
b | CPL+PL | -0.57 -1.68/+0.67 | 365 keV | -0.98 -0.61/+0.39 |    1.38 (81)
c |   PL   |       -----       |   ---   | -0.92 -0.98/+0.40 |    1.05 (84)

MCAL light curve and spectra in the different time intervals can be found
at:
http://www.agilescienceapp.it/notices/GRB210410A_AGILE-MCAL_intervals.png .

Additional analysis of AGILE data is in progress. Automatic MCAL GRB alert
Notices can be found at: https://gcn.gsfc.nasa.gov/agile_mcal.html.


GRB_name: GRB210406A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29799
SUBJECT: GRB 210406A: 10.4m GTC follow-up observation
DATE:    21/04/11 21:00:25 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

Y.-D. Hu, E. Fernandez-Garcia, A. J. Castro-Tirado, M.D. Caballero-Garcia, M. A. Castro Tirado (IAA-CSIC), V. Sokolov (SAO-RAS), I. Carrasco and A. Castellon (UMA) and  S. B. Pandey (ARIES), on behalf of a larger collaboration, report:

Following the detection of GRB 210406A by INTEGRAL (Mereghetti et al. GCNC 29767), we triggered the 10.4m GTC telescope equipped with OSIRIS in La Palma (Spain) starting on Apr 10 at 20:47 UT (~4.15 d after trigger). The 1.5 arcmin error region (Mereghetti et al. GCNC 29767) was covered by the two OSIRIS CCDs with an exception of a 9.4 arcsec gap in between.

For the optical candidate detected at Mondy Observatory (Belkin et al. GCNC 29775) a magnitude 22.45+-0.09 in r-band is measured. Since this value is consistent with the second epoch Mondy observation, a potential host galaxy cannot be excluded if this optical variability is finally confirmed although we notice that no X-ray afterglow has been reported by Swift/XRT at this position (D'Elia et al. GCNC 29785).

In addition to this, close to the source #3 position (6.4 arcsec error region) reported by Swift/XRT (D'Elia et al. GCNC 29785) we found two objects on the outskirts of it. The first one is located at RA: 8:50:00.18 DEC: +76:31:50.50 (J2000) for which we measure 22.96+-0.12 mag in r-band and seems to be recorded in Pan-STARRS DR2. A fainter object is found at RA: 8:50:01.42 DEC: +76:31:41.02 (J2000) for which we measure a magnitude of 24.00+-0.26 in r-band.

All magnitudes are calibrated with the Pan-STARRS catalog. Further observations are needed.

We thank the staff at Roque de Los Muchachos Observatory for their excellent support.


GRB_name: GRB210411C
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29800
SUBJECT: GRB 210411C: Enhanced Swift-XRT position
DATE:    21/04/11 21:08:26 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 318 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 210411C, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 296.61122, -39.39793 which is equivalent
to:

RA (J2000): 19h 46m 26.69s
Dec (J2000): -39d 23' 52.6"

with an uncertainty of 2.0 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB210411B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29801
SUBJECT: Fermi GRB 210411B: Global MASTER-Net observations report 
DATE:    21/04/11 21:45:12 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-SAAO robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 210411B ( Fermi GBM team, GCN 29792) errorbox  23474 sec after notice time and 23504 sec after trigger time at 2021-04-11 20:04:29 UT, with upper limit up to  19.5 mag. The observations began at zenith distance = 48 deg. The sun  altitude  is -47.0 deg. 

The galactic latitude b = -23 deg., longitude l = 287 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1589472

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   23535 | 2021-04-11 20:04:29 |         MASTER-SAAO | (08h 39m 30.90s , -77d 56m 23.8s) |   C |    60 | 19.1 |        
   23614 | 2021-04-11 20:05:48 |         MASTER-SAAO | (09h 17m 38.95s , -77d 58m 02.2s) |   C |    60 | 19.1 |        
   23694 | 2021-04-11 20:07:08 |         MASTER-SAAO | (06h 05m 46.43s , -77d 55m 48.7s) |   C |    60 | 19.2 |        
   23774 | 2021-04-11 20:08:28 |         MASTER-SAAO | (06h 44m 09.25s , -77d 56m 38.9s) |   C |    60 | 19.5 |        
   23853 | 2021-04-11 20:09:48 |         MASTER-SAAO | (06h 49m 34.90s , -69d 55m 53.0s) |   C |    60 | 19.3 |        
   23933 | 2021-04-11 20:11:07 |         MASTER-SAAO | (07h 13m 02.86s , -69d 56m 51.4s) |   C |    60 | 19.1 |        
   24013 | 2021-04-11 20:12:27 |         MASTER-SAAO | (08h 22m 55.69s , -69d 57m 59.8s) |   C |    60 | 19.3 |        
   24331 | 2021-04-11 20:17:45 |         MASTER-SAAO | (08h 49m 46.39s , -79d 56m 17.7s) |   C |    60 | 19.3 |        
   25214 | 2021-04-11 20:32:28 |         MASTER-SAAO | (06h 31m 44.71s , -79d 54m 54.6s) |   C |    60 | 19.5 |        
   25772 | 2021-04-11 20:41:47 |         MASTER-SAAO | (09h 17m 41.73s , -77d 57m 08.2s) |   C |    60 | 18.5 |        
   25852 | 2021-04-11 20:43:06 |         MASTER-SAAO | (06h 44m 10.04s , -77d 54m 52.8s) |   C |    60 | 18.7 |        
   25932 | 2021-04-11 20:44:26 |         MASTER-SAAO | (07h 12m 53.13s , -69d 55m 51.2s) |   C |    60 | 17.8 |        
   26331 | 2021-04-11 20:51:05 |         MASTER-SAAO | (06h 31m 40.60s , -79d 54m 22.4s) |   C |    60 | 16.8 |        
   28128 | 2021-04-11 21:20:02 |         MASTER-SAAO | (06h 40m 14.19s , -74d 54m 56.2s) |   C |   180 | 18.5 |        
   28328 | 2021-04-11 21:23:22 |         MASTER-SAAO | (06h 40m 12.18s , -74d 53m 09.6s) |   C |   180 | 17.6 |        
   28528 | 2021-04-11 21:26:42 |         MASTER-SAAO | (07h 20m 04.43s , -74d 54m 54.3s) |   C |   180 | 17.7 |        
   28727 | 2021-04-11 21:30:01 |         MASTER-SAAO | (07h 20m 07.24s , -74d 52m 59.5s) |   C |   180 | 18.2 |        
   28927 | 2021-04-11 21:33:21 |         MASTER-SAAO | (08h 07m 54.55s , -74d 54m 18.5s) |   C |   180 | 17.7 |        
   29127 | 2021-04-11 21:36:41 |         MASTER-SAAO | (08h 07m 54.94s , -74d 53m 12.7s) |   C |   180 | 17.6 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210411C
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29802
SUBJECT: GRB 210411C: LCO Optical Afterglow Candidate
DATE:    21/04/11 22:59:47 GMT
FROM:    Robert Strausbaugh at U. of the Virgin Islands  <robert.strausbaugh@uvi.edu>

R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (U. of the Virgin Islands/College of Marin) report on behalf of a larger collaboration:

We observed Swift GRB 210411C (Sbarrato, GCN 29794) with the LCO 1-m Sinistro instrument at the Siding Spring Observatory, Australia site, on April 11, from 16:18 to 16:42 UT (corresponding to 1.22 to 1.62 hours from the GRB trigger time) with the Bessel R and I filters.

We performed a series of 4x180s exposures in R and I. We detect an optical source in R and I band images at a location consistent the initial UVOT detection (Sbarrato, GCN 29794) and enhanced XRT position (Goad, GCN 29800), that is not present in either USNO or 2MASS catalogs.  Using the USNO-B.1 catalog as reference, we calculate the following magnitudes:

R = 18.51 +/- 0.03

I = 18.01 +/- 0.03

These magnitudes are not corrected for galactic extinction.  These magnitudes may also be contaminated by a bright foreground star.

R.S. is funded by NSF AST grant #1831682


GRB_name: GRB210411C
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29803
SUBJECT: GRB 210411C: BOOTES-4/MET optical upper limit
DATE:    21/04/11 23:14:20 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

Y.-D. Hu, E. Fernandez-Garcia, A. J. Castro-Tirado, M. D. Caballero-Garcia, M. A. Castro Tirado (IAA-CSIC), C. Perez del Pulgar (Univ. de Malaga), S. Guziy (Univ. of Nikolaev) and D. R. Xiong, Y. F. Fan, J. M. Bai, C. J. Wang, Y. X. Xin, X. H. Zhao (Yunnan Observatories of CAS) on behalf of a larger collaboration, report:

Following the detection of GRB 210411C by Swift (Sbarrato et al. GCNC 29794), follow-up observations at the 0.6m BOOTES-4/MET robotic telescope in Lijiang Astronomical Observatory (China) were performed starting on Apr 11, 20:52 UT (~5.8 hr after trigger) at high airmass. No new source is detected down to 19.6 mag at the optical afterglow position reported by UVOT (Sbarrato et al. GCNC 29794) and the 1.0m LCO in Siding Spring (Strausbaugh et al. GCNC 29802) in our co-added image (25x60 s, clear filter) confirming the fading in the optical range.

We thank the staff at Lijiang observatory for their excellent support.

[GCN OPS NOTE(12apr21):  Per author's request, the GRB name in the first sentence 
has been changed from "210406A" to 210411C".]


GRB_name: GRB210411C
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29804
SUBJECT: Swift GRB 210411C: Global MASTER-Net observations report 
DATE:    21/04/12 08:13:01 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-OAFA robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB 210411C ( T. Sbarrato et al., GCN 29794) errorbox  60730 sec after notice time and 60747 sec after trigger time at 2021-04-12 07:58:18 UT, with upper limit up to  19.0 mag. The observations began at zenith distance = 37 deg. The sun  altitude  is -38.0 deg. 

The galactic latitude b = -27 deg., longitude l =  1 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1589515

We obtain a following upper limits.  

Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   60837 |         MASTER-OAFA |   C |   180 | 19.0 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210410A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29805
SUBJECT: GRB 210410A: MITSuME Akeno optical upper limits
DATE:    21/04/12 10:29:30 GMT
FROM:    Katsuhiro L. Murata at Nagoya U  <murata@u.phys.nagoya-u.ac.jp>

K. L. Murata, R. Hosokawa, M. Niwano, N. Ito, H. Takamatsu, Y. Yatsu, and
N.Kawai (TokyoTech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 210410A (The Fermi GBM team et al. GCN
Circular #29777, A. Melandri  et al. GCN Circular #29778, V. Lipunov et al.
GCN Circular #29779, M. Jelinek et al. GCN Circular #29780, M. Arimoto et
al. GCN Circular #29781, A. Ursi et al. GCN Circular #29782, Nat Butler et
al. GCN Circular #29784, Nat Butler et al. GCN Circular #29786, Paul Kuin
et al. GCN Circular #29787, J. Wood et al. GCN Circular #29788, A. D'Ai  et
al. GCN Circular #29790, A. Y. Lien et al. GCN Circular #29793, A. Ridnaia
et al. GCN Circular #29797, A. Ursi  et al. GCN Circular #29798) with the
optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50
cm telescope of Akeno Observatory, Yamanashi, Japan. The observation with a
series of 60 sec exposures started at 2021-04-10 13:35 (9.7 hours after the
Fermi/GBM trigger). We stacked the images with good conditions. We did not
detect the optical afterglow reported previously (Jelinek et al. GCN
Circular #29780, Butler et al. GCN Circular #29784) in all three bands. We
obtained the 5-sigma limits of the stacked images as follows.

T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
10.0 14:00:15 1740 g'>19.3, Rc>19.6, Ic>19.0
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used the PS1 catalog for flux calibration.The magnitudes are expressed
in the AB system. The images were processed in real-time through the
MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1,
Pages 4-24; https://github.com/MNiwano/Eclaire).


GRB_name: GRB210411C
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29806
SUBJECT: GRB 210411C: VLT/X-shooter redshift
DATE:    21/04/12 10:46:55 GMT
FROM:    Daniele B Malesani at DTU Space  <malesani@space.dtu.dk>

A. de Ugarte Postigo (HETH/IAA-CSIC and DARK/NBI), B. Sbarufatti (PSU), 
D. Xu (NAO/CAS), J.-B. Vielfaure (APC, Paris University), D. B. Malesani 
(DTU Space), D. A. Kann (HETH/IAA-CSIC) V. D'Elia (ASI/SSDC, INAF/OAR), 
P. J. Pessi (FCAG/ESO), report on behalf of the Stargate consortium:

We observed the optical afterglow of GRB 210411C (Sbarrato et al., GCN 
29794) using the ESO VLT UT3 (Melipal) equipped with the X-shooter 
spectrograph. Our spectra cover the wavelength range 3000-21000 AA, and 
consist of 4 exposures by 1200 s each (8x600 s in the NIR). The 
observation mid time was 2021 Apr 12.33 UT (16.9 hr after the GRB).

In a 60 s image taken with the acquisition camera on Apr 12.294 UT, we 
detect the optical afterglow, for which we measure an AB magnitude r = 
21.69 +- 0.04 (calibrated against nearby stars from the SkyMapper 
catalog; Wolf et al. 2018, PASA, 35, 010; 
https:doi.org/10.4225/41/593620ad5b574).

We clearly detect continuum over the wavelength range 3520 - 17500 AA. A 
trough is visible around 4650 AA, which we identify as due to H I. From 
the detection of several narrow absorption features, which we interpret 
as due to, among others, Si II, Si II*, O I, C II, Si IV, C IV, Fe II, 
Al II, we infer a redshift z = 2.826. We also identify the FeII* 2396 
fine-structure transition, though at low S/N.

We acknowledge excellent support from the observing staff at Paranal, in 
particular Eleonora Sani and Bin Yang.

[GCN OPS NOTE(12apr2021):  Per author's request, GRB in the SUBJECT line
was changed from 210411A" to the correct name "210411C".]


GRB_name: GRB210411C
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29807
SUBJECT: GRB 210411C: Swift-XRT refined Analysis
DATE:    21/04/12 15:33:49 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

J. D. Gropp (PSU), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), P.A.
Evans (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB) and T.
Sbarrato report on behalf of the Swift-XRT team:

We have analysed 6.4 ks of XRT data for GRB 210411C (Sbarrato et al.
GCN Circ. 29794), from 66 s to 42.0 ks after the  BAT trigger. The data
comprise 136 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Goad et al. (GCN Circ. 29800).

The late-time light curve (from T0+5.4 ks) can be modelled with a
power-law decay with a decay index of alpha=1.49 (+/-0.17).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.66 (+0.19, -0.18). The
best-fitting absorption column is  1.2 (+0.4, -0.3) x 10^21 cm^-2, in
excess of the Galactic value of 8.1 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.84 (+0.14, -0.11)
and a best-fitting absorption column of 9.4 (+4.0, -1.3) x 10^20 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.6 x 10^-11 (4.3 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      9.4 (+4.0, -1.3) x 10^20 cm^-2
Galactic foreground: 8.1 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.84 (+0.14, -0.11)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01042398.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210411C
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29808
SUBJECT: GRB 210411C: ePESSTO+ NTT optical observations
DATE:    21/04/12 20:22:21 GMT
FROM:    Daniele B Malesani at DTU Space  <malesani@space.dtu.dk>

P. Pessi (ESO), G. Csoernyei, A. Holas, S. Taubenberger, C. Vogl (MPA 
Garching), A. Floers (GSI), G. Pignata (UNAB), J. Teffs (Liverpool), M. 
Dennefeld (IAP), D. B. Malesani (DTU Space), P. D'Avanzo (INAF/Brera), 
J. Anderson (ESO), T. MÃ¼ller Bravo (Southampton), T.-W. Chen 
(Stockholm), M. Gromadzki (Warsaw), C. Inserra (Cardiff), E. Kankare 
(Turku), M. Nicholl (Birmingham), O. Yaron (Weizmann), D. Young (QUB), 
E. Zimmerman (Weizmann) report:

We observed the optical afterglow of GRB 210411C (Sbarrato et al., GCN 
29794; Strausbaugh & Cucchiara, GCN 29802; de Ugarte Postigo et al., GCN 
29806) under the the advanced Public ESO Spectroscopic Survey for 
Transient Objects (ePESSTO+; see Smartt et al. 2015, A&A, 579, 40 and 
http://www.pessto.org ). The observations were performed on the ESO New 
Technology Telescope (NTT) at La Silla with the EFOSC2 instrument. A 
single 5-min exposure was acquired in the Gunn r filter, with mean epoch 
2021 Apr 12.234 UT (14.55 hr after the GRB).

The optical afterglow is well detected and we report the following 
coordinates (calibrated against the Gaia catalog):

RA = 19:46:26.83
Dec = -39:23:52.7

For the afterglow, we measure a magnitude R = 21.28 +- 0.04 (Vega), 
assuming R = 17.31 for the USNO star at RA = 19:46:25.68, Dec = 
-39:23:48.9 . An extra uncertainty of ~0.3 mag should be added to 
account for the photometric calibration error of the USNO catalog.


GRB_name: GRB210411C
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29809
SUBJECT: GRB 210411C: Chilescope optical observations
DATE:    21/04/12 20:40:48 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI), A. Pozanenko (IKI), M. Krugov (AFIF), N. Pankov (HSE) 
report on behalf of IKI-FuN follow-up collaboration:

We observed the Swift GRB 210411C (Sbarrato et al., GCN 29794) with 
Chilescope RC-1000 started on April 12 (UT) 07:43:39 in r'-filter. We 
clearly detected optical afterglow (Sbarrato et al., GCN 29794; 
Strausbaugh et al., GCN 29802; Hu et al., GCN 29803; Lipunov et al., GCN 
29804; de Ugarte Postigo et al., GCN 29806; Pessi et al., GCN 29808) in 
a stacked image with a total exposure of 3*600 seconds.

Preliminary photometry is following.

Date       UT start   t-T0       Filter Exp.   OT    Err.  UL(3sigma)
                      (mid, days)        (s)
2021-04-12 07:43:39   0.70333    r'     3*600  21.76 0.16  22.4

The photometry is based on nearby stars from the SkyMapper catalog
SMSS-DR1.1_id r
194633.88-392221.5 17.428
194648.73-392400.2 16.180


GRB_name: GRB210411C
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29810
SUBJECT: GRB 210411C: Swift-BAT refined analysis
DATE:    21/04/12 21:49:50 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
T. Sbarrato (INAF-OAB), M. Stamatikos (OSU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-60 to T+243 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 210411C (trigger #1042398)
(Sbarrato et al., GCN Circ. 29794).  The BAT ground-calculated position is
RA, Dec = 296.601, -39.399 deg which is
   RA(J2000)  =  19h 46m 24.2s
   Dec(J2000) = -39d 23' 57.8"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 79%.

The mask-weighted light curve shows a multi-peaked structure that
starts at ~T0 and ends at ~T+17 s. The two major peaks occur at ~T+4 s
and ~T+11 s, respectively. T90 (15-350 keV) is 12.80 +- 0.60 sec
(estimated error including systematics).

The time-averaged spectrum from T-0.45 to T+14.44 sec is best fit by a
power law
with an exponential cutoff.  This fit gives a photon index 1.60 +- 0.40,
and Epeak of 14.8 +- 10.8 keV (chi squared 51.24 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 1.2 +- 0.1 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+3.87 sec in the 15-150 keV band is
4.8 +- 0.3 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 2.62 +- 0.09 (chi squared 68.87 for 57 d.o.f.).  All the quoted errors
are at the 90% confidence level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1042398/BA/


GRB_name: GRB210411C
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29811
SUBJECT: GRB 210411C: Swift/UVOT Detection
DATE:    21/04/12 22:05:23 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

N. P. M. Kuin (UCL-MSSL) and Sbarrato (INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210411C
66 s after the BAT trigger (Sbarrato et al., GCN Circ. 29794).
A source consistent with the XRT position (Goad et al. GCN Circ. 29800)
is detected in the initial UVOT exposures. Further detections were
reported by Strausbaugh et al. (GCN Circ 29802)

The preliminary UVOT position is:
    RA  (J2000) =  19:46:26.81 = 296.61170 (deg.)
    Dec (J2000) = -39:23:52.2  = -39.39784 (deg.)
with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence).

Preliminary detections and 3-sigma upper limits using the UVOT photometric
system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures
are:

Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white               66          216          147         17.16 +/- 0.03
v                  609          801           39         17.43 +/- 0.18
b                  535          555           20         17.82 +/- 0.17
u                  279          528          246         17.82 +/- 0.07
w1                 658         1280           78        >19.7
m2                 633         5836           83        >19.6
w2                 584         5600          255        >20.1

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.081 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210410A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29812
SUBJECT: GRB 210410A: Swift/UVOT Upper Limits (revision)
DATE:    21/04/13 12:29:44 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

Paul Kuin (MSSL/UCL) reports on behalf of the Swift/UVOT team:

In our previous report (Kuin & Melandri, GCN Circ 29787) we made
an error computing T0, which affected our T_start and T_stop times.
Below are the corrected values.

Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)       mag 3-sigma UL

v                 1070         1095           19         >17.0
b                 4967         5055           85         >19.7
u                 4763         4960          197         >19.9
w1                4556         4755          197         >19.3
m2                4349         4548          197         >19.4
w2                1059         1071           12         >17.0


GRB_name: GRB210413A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29813
SUBJECT: GRB 210413A: GECAM detection
DATE:    21/04/13 12:34:35 GMT
FROM:    Y Q Zhang at IHEP  <yqzhang@ihep.ac.cn>

Y. Q. Zhang, S. L. Xiong, X. Y. Song, X. Y. Zhao, D. Y. Guo, Y. Huang,
S. Xiao, C. Cai, Y. Zhao, J. C. Liu, Q. B. Yi, W. C. Xue, Z. W. Guo,  
P. Wang, X. B. Li, W. X. Peng, R. Qiao, C. Zheng, C. W. Wang,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, J. J. He,
B. Li, C. Li, C. Y. Li, J. H. Li, Q. X. Li, X. Q. Li, Y. G. Li, X. H. Liang,
J. Y. Liao, J. C. Liu, X. J. Liu, Y. Q. Liu, F. J. Lu, Q. Luo, X. Ma,
G. Ou,  D. L. Shi, J. Y. Shi, L. M. Song, G. X. Sun, X. L. Sun, Y. L. Tuo,
J. Z. Wang, X. Y. Wen, Y. B. Xu, Y. P. Xu, S. Yang, M. Yao, B. X. Zhang,
C. Y. Zhang, D. L. Zhang, Fan Zhang, Fei Zhang, H. M. Zhang, K. Zhang,
P. Zhang, S. N. Zhang, Z. Zhang, S. Y. Zhao, S. J. Zheng, X. Zhou (IHEP),
report on behalf of GECAM team:

During the commissioning phase, GECAM-B triggered a long burst,
GRB 210413A, at 2021-04-13T01:07:25.600 UTC (denoted as T0).

According to the GECAM-B light curves in about 8 keV - 115 keV, 
this burst mainly consists of multiple pulses with duration of about 5 s.

Although the in-flight calibration of energy response and localization
has not been finalized yet, GECAM-B localized this burst to the 
following position (J2000):
Ra: 68.6 deg 
Dec: 11.3 deg 
Err: 3.6 deg (1-sigma, statistical only) 

The current systematic error of location is estimated to be several degrees
which could be minimized by the ongoing calibration. 

The GECAM light curve could be found here: 
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/multiLCvsE_tn210413_010724.pdf

The GECAM preliminary location could be found here:  
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_skymap_bdm_71975245_V01.png

Please note that all GECAM results here are preliminary. The final analysis
will be published in journal papers or GECAM online catalog.

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in
Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time),
which was funded by the Chinese Academy of Sciences (CAS).


GRB_name: GRB210415A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29814
SUBJECT: GRB 210415A: Fermi GBM Final Real-time Localization
DATE:    21/04/15 06:58:39 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 06:48:20 UT on 15 Apr 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210415A (trigger 640162105.095184 / 210415284).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 130.3, Dec = -37.9 (J2000 degrees, equivalent to J2000 08h 41m, -37d 53'), with a statistical uncertainty of 11.5 degrees.

The angle from the Fermi LAT boresight is 37.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210415284/quicklook/glg_skymap_all_bn210415284.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210415284/quicklook/glg_healpix_all_bn210415284.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210415284/quicklook/glg_lc_medres34_bn210415284.gif


GRB_name: GRB210415A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29815
SUBJECT: Fermi GRB 210415A: Global MASTER-Net observations report 
DATE:    21/04/15 07:15:08 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-OAFA robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 210415A ( Fermi GBM team, GCN 29814) errorbox  183 sec after notice time and 216 sec after trigger time at 2021-04-15 06:51:56 UT, with upper limit up to  17.9 mag. The observations began at zenith distance = 80 deg. The sun  altitude  is -51.8 deg. 

The galactic latitude b =  3 deg., longitude l = 259 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1592946

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

     246 | 2021-04-15 06:51:56 |         MASTER-OAFA | (09h 07m 34.52s , -35d 14m 21.0s) |   C |    60 | 17.6 |        
     326 | 2021-04-15 06:53:15 |         MASTER-OAFA | (09h 13m 34.85s , -33d 14m 59.7s) |   C |    60 | 17.6 |        
     405 | 2021-04-15 06:54:35 |         MASTER-OAFA | (09h 01m 52.73s , -37d 14m 56.7s) |   C |    60 | 17.5 |        
     485 | 2021-04-15 06:55:54 |         MASTER-OAFA | (09h 19m 53.44s , -31d 14m 12.4s) |   C |    60 | 17.7 |        
     564 | 2021-04-15 06:57:14 |         MASTER-OAFA | (08h 56m 37.35s , -39d 14m 03.0s) |   C |    60 | 17.6 |        
     644 | 2021-04-15 06:58:34 |         MASTER-OAFA | (09h 22m 12.49s , -37d 14m 26.1s) |   C |    60 | 17.7 |        
     724 | 2021-04-15 06:59:53 |         MASTER-OAFA | (09h 27m 17.12s , -35d 14m 49.3s) |   C |    60 | 17.7 |        
     803 | 2021-04-15 07:01:12 |         MASTER-OAFA | (08h 51m 35.77s , -41d 13m 57.9s) |   C |    60 | 17.9 |        
     882 | 2021-04-15 07:02:32 |         MASTER-OAFA | (08h 47m 08.04s , -43d 13m 58.0s) |   C |    60 | 17.9 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210410A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29816
SUBJECT: GRB 210410A: A twin of short GRB 090510 with complementary observations
DATE:    21/04/15 08:43:33 GMT
FROM:    Remo Rufinni at ICRA  <ruffini@icra.it>

 Y. Aimuratov, C.L. Bianco, L. Li, R. Moradi, F. Rastegar Nia, J.A.
Rueda, R. Ruffini,  N. Sahakyan, Y. Wang, S.S. Xue on behalf of  the
ICRANet team, report:

GRB 210410A has been announced as a likely long GRB (Fermi GBM Team
2021, GCN 29777), it has been also observed by Swift-XRT (A. Melandri
et al 2021, GCN 29778, and A. Dâ€™Ai et al, 2021, GCN 29790), by
Fermi-LAT (M. Arimoto et al 2021, GCN 29781), by AGILE (A. Ursi et al.
2021, GCN 29782), by Swift BAT (A. Y. Lien et al, 2021 GCN 29793) as
well as by Konus-Wind (A. Ridnaia et al 2021, GCN 29797). The
Fermi-GBM has determined T90=48 s in 50-300 keV (J. Wood et al 2021,
GCN 29788). A possible detection of the host galaxy at redshift z<3.6
was indicated by Butler et al 2021 (GCN 29784).

We here propose that GRB 210410A is a twin and covers the
complementary observation to the short GRB 090510, with T90=0.3 s. (R.
Ruffini et al 2016 ApJ 831 178).

We infer that GRB 210410A is a short GRB originating from a black hole
formation in view of its observed GeV emission (M. Arimoto et al
GCN29781) that and no supernova will be detected. We evidence for the
first time an angle dependence of the emission of short GRB: in the
polar observation for GRB 090510, with T90=0.3 s and in the equatorial
observation for GRB 210410A, with T90=48 s.

The spectroscopic determination of the redshift of the host galaxy is
essential for the determination of the GeV luminosity and consequently
the BH mass (R. Ruffini et al 2019 ApJ 886 82). We indicate the
relevance of the redshift determinations in the two enclosed figures.

"http://www.icranet.org/documents/GRB210410A-z=0.6-and-GRB090510-z=0.903.pdf"

"http://www.icranet.org/documents/GRB210410A-z=3.6-and-GRB090510-z=0.903.pdf"


GRB_name: GRB210410A
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29817
SUBJECT: GRB 210410A: AstroSat CZTI detection
DATE:    21/04/15 14:44:22 GMT
FROM:    Gaurav Waratkar at IIT Bombay  <gauravwaratkar24@gmail.com>

P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), S. Gupta
(IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao
(IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI
collaboration:

Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al, 2020,
arxiv:2011.07067) showed detection of a long GRB 210410A, which was also
detected by Fermi-GBM (GCN #29777, #29788), Swift-XRT (GCN #29778, #29790),
Fermi-LAT (GCN #29781), Swift-BAT (GCN #29793), Konus-Wind (GCN #29797) and
AGILE-MCAL (GCN #29798).

The source was clearly detected in the 20-200 keV energy range. The light
curve showed multiple peaks of emission with the strongest peak at
2021-04-10 00:53:16.50 UT. Quadrant D was noisy, and we exclude it from
further analysis. The measured peak count rate associated with the burst is
225 (+45, -16) cts/s above the background in the combined data of four
quadrants, with a total of 1808 (+239, -299) cts. The local mean background
count rate was 373  (+2, -2) cts/s. Using cumulative rates, we measure a
T90 of 20 (+6, -7) s.

It was also clearly detected in the CsI anticoincidence (Veto) detector in
the 100-500 keV energy range. The light curve showed multiple peaks of
emission with the strongest peak at 2021-04-10 00:53:15.867 UT. The
measured peak count rate is 1149 (+91, -57) cts/s above the background in
the combined Veto data of four quadrants, with a total of 8483 (+515, -574)
cts. The local mean background count rate was 1580 (+4, -4) cts/s. We
measure a T90 of 18 (+6, -4) s from the cumulative Veto light curve.

CZTI GRB detections are reported regularly on the payload site at
http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led
consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and
PRL. The Indian Space Research Organisation funded, managed and facilitated
the project.


GRB_name: GRB210411B
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29818
SUBJECT: GRB 210411B: AstroSat CZTI detection
DATE:    21/04/15 14:46:58 GMT
FROM:    Gaurav Waratkar at IIT Bombay  <gauravwaratkar24@gmail.com>

P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), S. Gupta
(IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao
(IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI
collaboration:

Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al, 2020,
arxiv:2011.07067) showed detection of a long GRB 210411B, which was also
detected by Fermi-GBM (GCN #29792).

The source was clearly detected in the 20-200 keV energy range. The light
curve showed multiple peaks of emission with the strongest peak at
2021-04-11 13:32:55.50 UT. Quadrant D was noisy, and we exclude it from
further analysis. The measured peak count rate associated with the burst is
117 (+47, -13) cts/s above the background in the combined data of four
quadrants, with a total of 1409 (+320, -296) cts. The local mean background
count rate was 492 (+2, -2) cts/s. Using cumulative rates, we measure a T90
of 27 (+4, -5) s.

CZTI GRB detections are reported regularly on the payload site at
http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led
consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and
PRL. The Indian Space Research Organisation funded, managed and facilitated
the project.


GRB_name: GRB210413B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29819
SUBJECT: GRB 210413B: Swift/BAT detection and probable localization of a short burst
DATE:    21/04/16 00:04:06 GMT
FROM:    Aaron Tohuvavohu at U Toronto  <aaron.tohu@gmail.com>

Swift/BAT did not successfully trigger on GRB 210413B (T0: 2021-04-13
23:46:52.45 UTC, Fermi/GBM TRIGGER 640050417).

The GUANO system is currently offline, thus no extended GUANO data is
available for this time, and so the sensitive GUANO MLL analysis
(DeLaunay et al. 2021, in prep) can not be run.

Swift/BAT triggered in real-time onboard in the rates domain (trigger
#1043009), but no strong source was found to be associated in the
onboard imaging. This 'failed trigger' resulted in 10s of BAT TTE data
being saved and sent to the ground.

The duration of the burst, as seen by BAT, is T90 = 1.088 s +/- 0.09 s.

In ground analysis of the available TTE data, we find a source using
typical imaging analysis, that is the likely location of the GRB, with
SNR 6 in the image domain.
The BAT position is
RA, Dec = 182.558 +55.965, which is:
    RA (J2000)     12h 10m 13.920s
    Dec (J2000)  +55d 57' 54.00"
with an estimated uncertainty of 3 arcminutes.

This location is consistent with the Fermi/GBM localization
distributed in the Final Position notice.

XRT and UVOT follow-up has been requested. Results of follow-up
observations will be reported in future circulars.


GRB_name: GRB210413B
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29821
SUBJECT: GRB 210413B: Swift ToO observations
DATE:    21/04/16 04:32:21 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a ToO observation of the Swift/BAT GRB 210413B. 
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021428

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Swift/BAT event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a 
GCN Circular after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210411C
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29823
SUBJECT: GRB 210411C: A very significant early X-ray afterglow
DATE:    21/04/16 15:47:13 GMT
FROM:    Remo Rufinni at ICRA  <ruffini@icra.it>

Y. Aimuratov, C.L. Bianco, L. Li, R. Moradi, F. Rastegar Nia, J.A. Rueda,
R. Ruffini,  N. Sahakyan, Y. Wang, S.S. Xue on behalf of the ICRANet team,
report:

GRB 210411C (trigger=1042398) with a redshift z=2.826 (A. de Ugarte Postigo
et al, 2021, GCN29806) was triggered and located by Swift Burst Alert
Telescope (BAT) (T. Sbarrato et al, 2021, GCN 29794) with T90=12.8 sec in
15-150 keV (C. B. Markwardt et al, 2021, GCN29810).

The corresponding luminosity light curves of Swift-BAT and Swift-XRT (J.D.
Gropp et al, 2021, GCN29807) show this source is a twin of GRB 190114C
(Ruffini et al, 2021, https://doi.org/10.1093/mnras/stab724). A new
additional feature is identified in the early luminosity of Swift-XRT data
of GRB 210411C (see enclosed Fig.1).

We recommend to check for the possible existence of a yet unobserved GeV
radiation and to follow up the late keV and possible GeV temporal power-law
luminosities.

Fig. 1:
http://www.icranet.org/documents/Swift_GRB210411C-Fermi_GRB190114C.pdf


GRB_name: GRB210413B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29825
SUBJECT: GRB 210413B: LOAO optical upper limit
DATE:    21/04/17 06:45:28 GMT
FROM:    Gregory SungHak Paek at SNU  <shpaek@astro.snu.ac.kr>

Gregory S.H. Paek (SNU ARC/SNU), Myungshin Im (SNU ARC/SNU), Chung-Uk Lee
(KASI), Seung-Lee Kim (KASI), Hyun-Il Sung (KASI) on behalf of a larger
collaboration

We searched for the optical counterpart of GRB 210413B (A. Tohuvavohu et
al. GCN #29819, and P. A. Evans et al., GCN #29821) with the 1-m class
telescope in Lemonsan Optical Astronomy Observatory (LOAO), one of
facilities of the GW EM-Counterpart Korean Observatory (GECKO).

We observed the center of Swift/BAT localization (RA, Dec = 182.558 +55.965),
but could not find any transient within the field of view of LOAO
(28.1'x28.1'). We calibrated flux with the PS1 catalog and used an AB
magnitude system.

------
Filter Date-obs[UT] Exp.time[s] Depth(5sigma)
B 2021-04-16T03:17:51.667 180*3 20.780
V 2021-04-16T03:27:54.933 180*3 20.347
R 2021-04-16T03:37:58.867 180*3 19.594
I 2021-04-16T03:47:55.800 180*3 19.293

We thank the LOAO opertator for performing the observation.
Gravitational-wave EM Counterpart Korean Observatory (GECKO) is a network
of 10+ 0.5m to 1m class telescopes over the world.


GRB_name: GRB210413B
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29827
SUBJECT: GRB 210413B: Swift-XRT observations
DATE:    21/04/17 20:07:06 GMT
FROM:    Antonino D'Ai at IASF-PA  <antonino.dai@inaf.it>

J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), J.P. Osborne (U.
Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), T.
Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), M.G. Bernardini
(INAF-OAB), B. Sbarufatti (PSU) and P.A. Evans (U. Leicester) report on
behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Swift/BAT-detected burst GRB 210413B (Swift/BAT did not successfully
trigger on GRB 210413B et al. GCN Circ. 29819), collecting 4.9 ks of
Photon Counting (PC) mode data between T0+185.0 ks and T0+206.7 ks. 

One uncatalogued X-ray source has been detected consistent with being
within 394 arcsec of the Swift/BAT position, it is below the RASS limit
and shows no definitive signs of fading. Therefore, at the present time
we cannot confirm this as the afterglow. Details of this source are
given below:

Source 1:
  RA (J2000):  182.5333  =  12:10:7.98
  Dec (J2000): +56.0497  =  +56:02:59.0
  Error: 5.7 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: (4.5 +/- 1.2)e-3 ct s^-1  
  Distance: 309 arcsec from Swift/BAT position.
  Flux: (1.42 +/- 0.39)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Three uncatalogued sources were also detected too far from the GRB
position to be likely afterglow candidates.

The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
https://www.swift.ac.uk/ToO_GRBs/00021428.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210419A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29828
SUBJECT: GRB 210419A: Swift detection of a burst
DATE:    21/04/19 07:11:30 GMT
FROM:    Kim Page at U.of Leicester  <klp5@leicester.ac.uk>

S. Laha (GSFC/UMBC/CRESST), E. Ambrosi (INAF-IASFPA),
A. D'Ai (INAF-IASFPA), V. D'Elia (SSDC & INAF-OAR),
J. A. Kennea (PSU), K. L. Page (U Leicester) and D. M. Palmer (LANL)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 06:53:41 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210419A (trigger=1044032).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 86.862, -65.539 which is 
   RA(J2000) = 05h 47m 27s
   Dec(J2000) = -65d 32' 20"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is usual for an image trigger, no
obvious variation is visible in the immediately-available lightcurve. 

The XRT began observing the field at 06:55:49.0 UT, 127.9 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 86.85414,
-65.50357 which is equivalent to:
   RA(J2000)  = 05h 47m 24.99s
   Dec(J2000) = -65d 30' 12.9"
with an uncertainty of 3.5 arcseconds (radius, 90% containment). This
location is 128 arcseconds from the BAT onboard position, within the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
https://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (7.76 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 5.3
(+3.15/-2.74) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 1.57e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 136 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.075. 

This source lies within the current (Sector 37) field-of-view of TESS camera 4. 

Burst Advocate for this burst is S. Laha (sib.laha AT gmail.com). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB210419A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29829
SUBJECT: GRB 210419A: LCO Optical Upper Limit
DATE:    21/04/19 15:40:31 GMT
FROM:    Robert Strausbaugh at U. of the Virgin Islands  <robert.strausbaugh@uvi.edu>

R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (U. of the Virgin Islands/College of Marin) report on behalf of a larger collaboration:

We observed Swift GRB 210419A (Laha, et al., GCN 29828) with the LCO 1-m Sinistro instrument at the Siding Spring Observatory, Australia site, on April 19, from 08:33 to 08:57 UT (corresponding to 1.67 to 2.1 hours from the GRB trigger time) with the Bessel R and I filters.

We performed a series of 4x180s exposures in R and I. We do not detect any uncatalogued optical source in the coadded images within the XRT error region (Laha, et al., GCN 29828).  Using the USNO-B.1 catalog as reference, we calculate the following upper limits:

R>21.91

I>21.16

These magnitudes are not corrected for galactic extinction.

R.S. is funded by NSF AST grant #1831682


GRB_name: GRB210419A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29830
SUBJECT: GRB 210419A: Enhanced Swift-XRT position
DATE:    21/04/19 19:38:17 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 2647 s of XRT Photon Counting mode data and 4 UVOT
images for GRB 210419A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 86.85096, -65.50250 which is equivalent
to:

RA (J2000): 05h 47m 24.23s
Dec (J2000): -65d 30' 09.0"

with an uncertainty of 2.0 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB210419B
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29831
SUBJECT: GRB 210419B: Fermi GBM Final Real-time Localization
DATE:    21/04/19 21:20:46 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 21:10:28 UT on 19 Apr 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210419B (trigger 640559433.454802 / 210419882).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 307.1, Dec = -0.1 (J2000 degrees, equivalent to J2000 20h 28m, 0d 06'), with a statistical uncertainty of 1.4 degrees.

The angle from the Fermi LAT boresight is 18.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210419882/quicklook/glg_skymap_all_bn210419882.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210419882/quicklook/glg_healpix_all_bn210419882.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210419882/quicklook/glg_lc_medres34_bn210419882.gif


GRB_name: GRB210419A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29832
SUBJECT: Swift GRB 210419A: Global MASTER-Net observations report 
DATE:    21/04/19 23:36:30 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-OAFA robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB 210419A ( S. Laha et al., GCN 29828) errorbox  58845 sec after notice time and 58929 sec after trigger time at 2021-04-19 23:15:50 UT, with upper limit up to  18.1 mag. Observations started at twilight.  The observations began at zenith distance = 43 deg. The sun  altitude  is -14.8 deg. 

The galactic latitude b = -31 deg., longitude l = 275 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1595763

We obtain a following upper limits.  

Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   59019 |         MASTER-OAFA |   C |   180 | 17.9 |        
   59305 |         MASTER-OAFA |   C |   180 | 18.1 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210419B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29833
SUBJECT: Fermi GRB 210419B: Global MASTER-Net observations report 
DATE:    21/04/20 00:00:07 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-Kislovodsk robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 210419B ( Fermi GBM team, GCN 29831) errorbox  8248 sec after notice time and 8274 sec after trigger time at 2021-04-19 23:28:23 UT, with upper limit up to  16.1 mag. The observations began at zenith distance = 71 deg. The sun  altitude  is -27.1 deg. 

The galactic latitude b = -22 deg., longitude l = 45 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1596170

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

    8305 | 2021-04-19 23:28:23 |   MASTER-Kislovodsk | (20h 27m 02.66s , +00d 07m 45.8s) |   C |    60 | 13.7 |        
    8543 | 2021-04-19 23:32:21 |   MASTER-Kislovodsk | (20h 19m 02.82s , +00d 06m 53.2s) |   C |    60 | 16.1 |        
    8860 | 2021-04-19 23:37:38 |   MASTER-Kislovodsk | (20h 19m 55.36s , +02d 08m 29.6s) |   C |    60 | 14.7 |        
    8940 | 2021-04-19 23:38:58 |   MASTER-Kislovodsk | (20h 27m 46.29s , -01d 51m 11.2s) |   C |    60 | 14.2 |        
    9257 | 2021-04-19 23:44:15 |   MASTER-Kislovodsk | (20h 27m 02.09s , +00d 07m 54.1s) |   C |    60 | 15.1 |        
    9337 | 2021-04-19 23:45:35 |   MASTER-Kislovodsk | (20h 35m 01.94s , +00d 08m 45.7s) |   C |    60 | 15.0 |        
    9496 | 2021-04-19 23:48:14 |   MASTER-Kislovodsk | (20h 19m 07.83s , +00d 07m 34.0s) |   C |    60 | 12.6 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210419C
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29834
SUBJECT: GRB 210419C: Swift detection of a burst
DATE:    21/04/20 00:45:40 GMT
FROM:    Michael Moss at George Washington U  <mikejmoss3@gmail.com>

M. J. Moss (GWU), V. D'Elia (SSDC & INAF-OAR), C. Gronwall (PSU),
J.D. Gropp (PSU), J. A. Kennea (PSU), N. J. Klingler (PSU),
N. P. M. Kuin (UCL-MSSL), S. Laha (GSFC/UMBC/CRESST),
A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), M. H. Siegel (PSU)
and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels
Swift Observatory Team:

At 23:27:49 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210419C (trigger=1044236).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 212.968, 35.999 which is 
   RA(J2000) = 14h 11m 52s
   Dec(J2000) = +35d 59' 56"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty). Currently, we only have limited BAT light curve data. 
The available light curve from ~T+110 s to ~T+400 s does
not show any significant structure. 

Due to lack of data, we do not have an accurate XRT position. However our current
best estimate for the GRB position is RA/Dec(J2000) = 212.96009,
+36.0096, which is equivalent to:

RA(J2000): 14h 11m 50.4s
Dec(J2000): 36d 00m 34.6s

Uncertainty of this position is unclear. We await ground
processed data to report an accurate position for this GRB. 

UVOT took a finding chart exposure of â€‹95â€‹ seconds with the â€‹Uâ€‹ filter
startingâ€‹ around 340 â€‹seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.0â€‹1â€‹. 

Burst Advocate for this burst is M. J. Moss (mikejmoss3 AT gmail.com). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB210419A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29835
SUBJECT: GRB 210419A: Swift-XRT refined Analysis
DATE:    21/04/20 02:38:59 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), J.P. Osborne
(U. Leicester), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) ,
M. Capalbi (INAF-IASFPA), B. Sbarufatti (PSU), D.N. Burrows (PSU), J.
D. Gropp (PSU) and S. Laha report on behalf of the Swift-XRT team:

We have analysed 6.8 ks of XRT data for GRB 210419A (Laha et al. GCN
Circ. 29828), from 134 s to 64.1 ks after the  BAT trigger. The data
comprise 143 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Osborne et al. (GCN Circ. 29830).

The late-time light curve (from T0+5.5 ks) can be modelled with a
power-law decay with a decay index of alpha=1.0 (+/-0.3).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.71 (+0.11, -0.10). The
best-fitting absorption column is  1.4 (+0.4, -0.3) x 10^21 cm^-2, in
excess of the Galactic value of 7.8 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.60 (+0.29, -0.27)
and a best-fitting absorption column of 1.9 (+0.7, -0.6) x 10^21 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 2.6 x 10^-11 (4.8 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.9 (+0.7, -0.6) x 10^21 cm^-2
Galactic foreground: 7.8 x 10^20 cm^-2
Excess significance: 2.9 sigma
Photon index:      2.60 (+0.29, -0.27)

If the light curve continues to decay with a power-law decay index of
1.0, the count rate at T+24 hours will be 4.3 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x
10^-13 (2.1 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01044032.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210420A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29837
SUBJECT: GRB 210420A: Fermi GBM Final Real-time Localization
DATE:    21/04/20 05:19:45 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 05:09:29 UT on 20 Apr 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210420A (trigger 640588174.204176 / 210420215).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 253.4, Dec = 12.2 (J2000 degrees, equivalent to J2000 16h 53m, 12d 11'), with a statistical uncertainty of 21.8 degrees.

The angle from the Fermi LAT boresight is 80.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210420215/quicklook/glg_skymap_all_bn210420215.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210420215/quicklook/glg_healpix_all_bn210420215.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210420215/quicklook/glg_lc_medres34_bn210420215.gif


GRB_name: GRB210419A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29838
SUBJECT: GRB 210419A: Swift-BAT refined analysis
DATE:    21/04/20 14:18:19 GMT
FROM:    Sibasish Laha at GSFC  <sibasish.laha@nasa.gov>

D. M. Palmer (LANL), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210419A (trigger #1044032)
(Laha et al., GCN Circ. 29828).  The BAT ground-calculated position is
RA, Dec = 86.912, -65.452 deg which is
   RA(J2000)  =  05h 47m 38.9s
   Dec(J2000) = -65d 27' 07.2"
with an uncertainty of 2.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 61%.

The BAT light curve showed a complex structure with a duration of about ~100 sec.
T90 (15-350 keV) is 64.43 +- 11.69 sec (estimated error including systematics).

The time-averaged spectrum from T+21.92 to T+95.01 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.17 +- 0.24.  The fluence in the 15-150 keV band is 7.8 +- 1.2 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T+41.82 sec in the 15-150 keV band
is 0.6 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1044032/BA/


GRB_name: GRB210419C
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29839
SUBJECT: GRB 210419C: Enhanced Swift-XRT position
DATE:    21/04/20 14:59:26 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 2102 s of XRT Photon Counting mode data and 3 UVOT
images for GRB 210419C, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 212.96251, +36.00741 which is equivalent
to:

RA (J2000): 14h 11m 51.00s
Dec (J2000): +36d 00' 26.7"

with an uncertainty of 2.4 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB210419C
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29840
SUBJECT: GRB 210419C: KAIT Optical Upper Limit
DATE:    21/04/20 15:17:16 GMT
FROM:    Weikang Zheng at UC Berkeley  <weikang@berkeley.edu>

WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on

behalf of the KAIT GRB team:


The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at

Lick Observatory, responded to Swift GRB 210419C (Moss et al.,

GCN 29834) starting at 6.87 hours after the burst. A total of

30x60s images were obtained in the clear (roughly R) filters.

We do not detect any new source within the enhanced XRT error circle

(Beardmore et al., GCN 29839) in the co-add images, down to a limiting

magnitude of ~21.5 mag calibrated to the PS1 catalog.


GRB_name: GRB210419A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29841
SUBJECT: GRB 210419A: Swift/UVOT Upper Limits
DATE:    21/04/20 15:49:41 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M. H. Siegel (PSU) and S. L. Laha (GSFC/UMBC/CRESST)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210419A
136 s after the BAT trigger (Laha et al., GCN Circ. 29828).
No optical afterglow consistent with the XRT position
(Osborne et al., GCN Circ 29830)
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           136          286          147         >18.1
u_FC               294          544          246         >17.9
white              136         1027          333         >18.1
v                  627         1079           58         >17.5
b                  550          746           39         >17.7
u                  294          721          265         >17.9
w1                 677          871           39         >17.8
m2                 651         1103           58         >18.3
w2                 119         1053           67         >19.3

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.075 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210419C
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29842
SUBJECT: GRB 210419C: Montarrenti Observatory Upper Limit
DATE:    21/04/20 16:21:43 GMT
FROM:    Simone Leonini at Monarrenti Obs  <s.leonini@iol.it>

Simone Leonini, M. Conti, P. Rosi and L.M. Tinjaca Ramirez (Montarrenti Observatory, Siena, Italy) report:

We observed the field of GRB210419C (Swift trigger 1044236, M.J. Moss et al., GCN Circ. 29834) with the automatic 0.53m RC telescope + U47 detector at Montarrenti Observatory (Siena, Italy, IAU code C88).

The observations were started under variable weather conditions at 2021-04-20 01:48:32 UT (3.780s after notice) stacking 12x30s clear filter CCD exposures.

We have not found optical transient within the error-box of the enhanced Swift-XRT position (RA 14h 11m 51.00s, Dec +36d 00m 26.7s - J2000).
Mag. upper limit R = 20.40+/-0.15


Magnitudes were obtained using Astrometrica software using USNO-B1 catalogue and are not corrected for galactic extinction.

Our non-detection is consistent with the limits reported by MASTER-Net (Lipunov et al, GCNC 29836) and KAIT (W.K. Zheng and A.V. Filippenko, GCNC 29840).


GRB_name: GRB210419C
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29843
SUBJECT: GRB 210419C: RATIR Optical and NIR Upper Limits
DATE:    21/04/20 16:34:17 GMT
FROM:    Nat Butler at Az State U  <natbutler@asu.edu>

Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William
H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier
Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora
Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), JesÃºs
GonzÃ¡lez (UNAM), Carlos RomÃ¡n-ZÃºÃ±iga (UNAM), Harvey Moseley (GSFC), John
Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report:

We observed the field of GRB 210419C (Moss, et al., GCN 29834) with the
Reionization and Transients Infrared Camera (RATIR) on the 1.5m Harold
Johnson Telescope at the Observatorio AstronÃ³mico Nacional on Sierra San
Pedro MÃ¡rtir from 2021/04 20.14 to 2021/04 20.50 UTC (2.58 to 11.15 hours
after the BAT trigger), obtaining a total of 4.53 hours exposure in the r
and i bands and 1.89 hours exposure in the Z, Y, J, and H bands.

We do not detect any sources within the enhanced XRT error region
(Beardmore, et al. GCN 29839).  In comparison with the SDSS DR9 and 2MASS
catalogs, we obtain the following upper limits (3-sigma):

  r     > 23.60
  i     > 23.53
  Z     > 22.31
  Y     > 20.10
  J     > 22.21
  H     > 21.87

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.

We thank the staff of the Observatorio AstronÃ³mico Nacional in San Pedro
MÃ¡rtir.


GRB_name: GRB210420B
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29844
SUBJECT: GRB 210420B: Swift detection of a burst
DATE:    21/04/20 19:34:55 GMT
FROM:    Kim Page at U.of Leicester  <klp5@leicester.ac.uk>

M. J. Moss (GWU), P. A. Evans (U Leicester), C. Gronwall (PSU),
J.D. Gropp (PSU), J. A. Kennea (PSU), K. L. Page (U Leicester) and
B. Sbarufatti (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

BAT triggered on GRB 210420B (trigger 1044382) at some time before 18:50
UT. Due to telemetry gaps, we have only XRT data for this burst and
therefore at the present time cannot give a precise trigger time, or
information about the BAT light curve. The most likely trigger time is
between 18:20 and 18:50 UT. Once the full dataset has been downlinked we
will be able to derive a precise trigger time and analyse the BAT light
curve. 

Using promptly downlinked data we find an uncatalogued X-ray source
located at RA, Dec 254.32245, 42.56951 which is equivalent to:
   RA(J2000)  = 16h 57m 17.39s
   Dec(J2000) = +42d 34' 10.2"
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This
position may be improved as more data are received; the latest position
is available at https://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (2.09 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 2.1
(+1.75/-1.59) x 10^21 cm^-2 (90% confidence). 

Burst Advocate for this burst is M. J. Moss (mikejmoss3 AT gmail.com). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB210420B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29845
SUBJECT: GRB 210420B: MASTER optical counterpart detection
DATE:    21/04/20 20:36:01 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, V.Kornilov, E.Gorbovskoy, A.Chasovnikov, P.Balanutsa,V.Vladimirov, A.Kuznetsov,
D. Vlasenko, N.Tiurina, I.Gorbunov,  D.Zimnukhov, V.Senik,V.Topolev,
F.Balakin, D.Cheryasov (Lomonosov Moscow State University,SAI, PhysicsDepartment),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev (Irkutsk State University, API),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)

MASTER Global robotic net (MASTER-Net:http://observ.pereplet.ru Lipunov etal.,2010,Advances in Astronomy,2010,30L)
started GRB 210420B (Swift trigger 1044382 Moss  et al. GCN 29844,Ttrigger=2021-04-20 18:20-50UT)
at MASTER-Kislovodsk at 2021-04-20 20:01:24UT

There is optical counterpart (changing)
at RA,Dec(2000)= 16h 57m 18.23s ,+42d 34m 11s.8 +-1"
MASTER OT J165718.23+423411.8
found by MASTER auto-detection system 
with m_OT~19 at 2021-04-20 20:05:23TU

Observation started at alert altitude 45deg.


GRB_name: GRB210420B
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29846
SUBJECT: GRB 210420B: Optical observations
DATE:    21/04/20 20:37:21 GMT
FROM:    Arto Oksanen at Nyrola Obs., Finland  <oksanen@nyrola.jklsirius.fi>

A. Oksanen (Hankasalmi observatory) report on behalf a larger collaboration:

We observed the field of the Swift GRB 210420B (Page et al., GCN 29844)
using the 0.40 m remote controlled RC telescope of Hankasalmi observatory 
equipped with the SBIG STX-16803 CCD camera. Total of 25 exposures of 60 s 
each were secured in the clear filter, starting on 2021 April 19:44:58 UT. 

A candidate afterglow is clearly detected in the XRT error circle with 
coordinates (J2000):

RA = 16:57:18.0
DEC = +42:34:12.6

Its magnitude is r = 17.97 +- 0.05 , calibrated against a nearby star
from SDSS. This object is not visible in the Digitized Sky Survey R band
images.

We consider this object as a viable afterglow candidate to GRB 210420B,
but a confirmation is necessary to assess variability. Further
observations are planned.


GRB_name: GRB210420B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29847
SUBJECT: GRB 210420B: BOOTES-4/MET optical afterglow detection
DATE:    21/04/20 21:14:16 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

Y.-D. Hu, T.-R. Sun, E. Fernandez-Garcia, A. J. Castro-Tirado, M.D. Caballero-Garcia, M. A. Castro Tirado (IAA-CSIC), C. Perez del Pulgar, A. Castellon, I. Carrasco (Univ. de Malaga), S. Guziy (Univ. of Nikolaev) and D. R. Xiong, Y. F. Fan, J. M. Bai, C. J. Wang, Y. X. Xin, X. H. Zhao (Yunnan Observatories of CAS) on behalf of a larger collaboration, report:

Following the detection of GRB 210420B by Swift (Moss et al. GCNC 29844), we triggered the 0.6m BOOTES-4/MET robotic telescope at Lijiang Astronomical Observatory (China) in order to follow up this event, starting on Apr 20, 19:51 UT. A series of images in clear filter was obtained. An uncatalogued optical source is found within the XRT position (Moss et al. GCNC 29844), for which we measure a magnitude of 17.9 +/- 0.1, calibrated against nearby stars in the USNO-B2 catalogue. This is consistent with the findings from MASTER (Lipunov et al, GCNC 29845) and Hankasalmi (Oksanen et al, GCNC 29846). Further observations are ongoing.

We thank the staff at Lijiang observatory for their excellent support.


GRB_name: GRB210420B
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29848
SUBJECT: GRB 210420B: AST3-3 YaoAn Optical Observation
DATE:    21/04/21 00:08:17 GMT
FROM:    Tianrui Sun at Purple Mountain Obs,CAS  <trsun@pmo.ac.cn>

Tianrui Sun(Purple Mountain Observatory), Lei Hu, Maokai Hu, Xuefeng Wu, Lei Liu, Kelai Meng, Xiaoyan Li(Nanjing Institute of Astronomical Observation Technology), Zhengyang Li, Xiangyan Yuan, Lifan Wang(TAMU), Xiaofeng Wang (Tsinghua University), report on behalf the AST3 Team:


Following the detection of GRB210420B by Swift (Moss et al. GCN 29844), we use Antarctic Survey Telescope 3-3 at YaoAn Astronomy Observation(China, Yunnan) to follow up. We observed 80 images in the g-band and exposure time in 60 seconds. The observation started at 2021-04-20T20:07:30.596 and ends at 2021-04-20T21:42:43.897. Within the candidate position (A. Oksanen et al. GCN 29846), we detected the source with 16.9 mag at 2021-04-20T20:07:30.596 and 17.5 mag at 2021-04-20T21:42:43.897. 


GRB_name: GRB210421A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29849
SUBJECT: GRB 210421A: Swift detection of a burst
DATE:    21/04/21 00:39:04 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

M. J. Moss (GWU), S. D. Barthelmy (GSFC), C. Gronwall (PSU),
J.D. Gropp (PSU), J. A. Kennea (PSU), S. Laha (GSFC/UMBC/CRESST),
A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (PSU) and
A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 00:27:30 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210421A (trigger=1044426).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 104.908, +4.934, which is 
   RA(J2000)  =  06h 59m 38s
   Dec(J2000) = +04d 56' 03"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of about 40 sec.  The peak count rate
was ~1500 counts/sec (15-350 keV), at ~2 sec after the trigger. 

The XRT began observing the field at 00:28:58.1 UT, 87.8 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 104.87569, 4.92168 which
is equivalent to:
   RA(J2000)  = 06h 59m 30.17s
   Dec(J2000) = +04d 55' 18.0"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 124 arcseconds from the BAT onboard position, within the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
https://www.swift.ac.uk/sper.  We cannot determine whether the source
is fading at the present time. No spectrum from the promptly downlinked
event data is yet available to determine the column density. 

The initial flux in the 0.1 s image was 1.51e-08 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 96 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the large, but uncertain, extinction expected. 

Burst Advocate for this burst is M. J. Moss (mikejmoss3 AT gmail.com). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB210421A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29850
SUBJECT: Swift GRB 210421A: Global MASTER-Net observations report 
DATE:    21/04/21 00:42:22 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-OAFA robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB 210421A ( M. J. Moss et al., GCN 29849) errorbox  13 sec after notice time and 47 sec after trigger time at 2021-04-21 00:28:17 UT, with upper limit up to  17.1 mag. The observations began at zenith distance = 54 deg. The sun  altitude  is -30.5 deg. 

The galactic latitude b =  5 deg., longitude l = 210 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1597889

We obtain a following upper limits.  

Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

      52 |         MASTER-OAFA |   C |    10 | 16.4 |        
      82 |         MASTER-OAFA |   C |    10 | 16.4 |        
     116 |         MASTER-OAFA |   C |    20 | 16.8 |        
     160 |         MASTER-OAFA |   C |    30 | 17.0 |        
     215 |         MASTER-OAFA |   C |    40 | 17.1 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210420B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29851
SUBJECT: GRB 210420B: Montarrenti Observatory optical afterglow detection
DATE:    21/04/21 01:21:44 GMT
FROM:    Simone Leonini at Monarrenti Obs  <s.leonini@iol.it>

Simone Leonini, M. Conti, P. Rosi and L.M. Tinjaca Ramirez (Montarrenti Observatory, Siena, Italy) report:

We observed the field of GRB 210420B (Swift trigger 1044382, M.J. Moss et al., GCN Circ. 29844) with the automatic 0.53m RC telescope + U47 detector at Montarrenti Observatory (Siena, Italy, IAU code C88).

The observations were started under good weather conditions at 2021-04-20 23:46:05 UT (approximately 4 hours after notice) stacking 5x60s R filter CCD exposures for each run.

The optical afterglow was clearly detected as follows:

2021 Apr 20.99207 UT (23:48:35 mid-time) R=19.0 +/-0.13
2021 Apr 21.03089 UT (00:44:29 mid-time) R=19.2 +/-0.14

Preliminary magnitudes were obtained using Astrometrica software using USNO-B1 catalogue for positions and photometry. An ensemble between 83 and 76 stars were used for the magnitude and astrometric comparison. Measures are not corrected for galactic dust extinction.

The position of the GRB (within the error box given by Swift) is the following:

RA (J2000) 16h 57m 18.05s +/-0.14
Decl. (J2000) +42Â° 34' 12.0" +/-0.13

Our detection is consistent with these reported by MASTER-Net (Lipunov et al, GCNC 29845), Hankasalmi Observatory (Oksanen, GCNC 29846), BOOTES-4 (Hu. et al., GCN 29847) and AST3-3 (Sun et al., GCN 29848).
Further observations are ongoing.


GRB_name: GRB210420B
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29852
SUBJECT: GRB 210420B: Multiband photometry from NOT
DATE:    21/04/21 01:42:40 GMT
FROM:    Antonio de Ugarte Postigo at IAA-CSIC  <deugarte@iaa.es>

A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), D. B. Malesani (DTU
Space), E. Knudstrup (NOT, Aarhus Univ.) report on behalf of a larger
collaboration:

We observed the afterglow of GRB 210420B (Moss et al. GCN 29844;
Lipunov et al. GCN 29845; Oksanen GCN 29846; Hu et al. GCN 29847; 
Sun et al. GCN 29848; Leonini et al. GCN 29851) with ALFOSC at the 
2.5 m Nordic Optical Telescope at Roque de los Muchachos Observatory 
(La Palma, Spain). The observation consisted of 3x100 s imaging in g, r 
and i bands, and 5x100 s in z-band and started at 00:13 UT.

The afterglow is well detected in individual images in all bands at
the following coordinates (J2000) calibrated with Gaia, and with an
uncertainty estimated at 0.3":

R.A. = 16:57:18.00
Dec. = +42:34:12.1

In a preliminary analysis we measure the following AB magnitudes, as
compared with 3 field stars from the SDSS catalogue:

g = 19.45 +/- 0.04
r =  19.32 +/- 0.04
i = 19.18 +/- 0.04
z = 19.03 +/- 0.07


GRB_name: GRB210420B
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29853
SUBJECT: GRB 210420B: Redshift from GTC
DATE:    21/04/21 01:45:21 GMT
FROM:    Antonio de Ugarte Postigo at IAA-CSIC  <deugarte@iaa.es>

A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), M. Blazek, 
C. Thoene, D. A. Kann, J. F Agui Fernandez (all HETH/IAA-CSIC), 
and S. Geier (GTC, IAC) report:

We observed the afterglow of GRB 210420B (Moss et al. GCN 
29844; Lipunov et al. GCN 29845; Oksanen GCN 29846; Hu et al. 
GCN 29847; Sun et al. GCN 29848; Leonini et al. GCN 29851; 
de Ugarte Postigo GCN 29852) with OSIRIS at the 10.4m GTC 
telescope, at the Roque de los Muchachos Observatory (La Palma, 
Spain). Observations consisted of 2x600 s spectroscopy with grism 
R1000B, covering the spectral range between 3700 and 7800 AA.

The spectrum shows a strong continuum with weak absorption 
features that we identify as due to FeII, MgII and MgI at a common 
redshift of z = 1.400, which we interpret as the redshift of the GRB.


GRB_name: GRB210420B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29854
SUBJECT: GRB 210420B: update on the BAT trigger time
DATE:    21/04/21 02:52:39 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

A. Y. Lien (GSFC/UMBC), M. J. Moss (GWU),
and A. Tohuvavohu (U Toronto)
report on behalf of the Neil Gehrels Swift
Observatory Team:

We received further data from recent telemetry downlink,
The trigger time for GRB 210420B (Swift trigger #1044382;
Moss et al., GCN Circ. 29844) is
2021-04-20T18:34:37 UTC.

The burst duration is at least 30 seconds, the full data
products will allow a complete duration estimate.


GRB_name: GRB210420A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29855
SUBJECT: Fermi GRB 210420A: Global MASTER-Net observations report 
DATE:    21/04/21 03:00:27 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-IAC robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Spain (IAC Teide Observatory) started inspect of the Fermi GRB 210420A ( Fermi GBM team, GCN 29837) errorbox  76671 sec after notice time and 76698 sec after trigger time at 2021-04-21 02:27:47 UT, with upper limit up to  18.0 mag. The observations began at zenith distance = 19 deg. The sun  altitude  is -45.1 deg. 

The galactic latitude b = 31 deg., longitude l = 31 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1596846

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   76728 | 2021-04-21 02:27:47 |          MASTER-IAC | (16h 48m 60.00s , +28d 09m 03.3s) |   C |    60 | 18.0 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210419C
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29856
SUBJECT: GRB 210419C: Swift-BAT refined analysis
DATE:    21/04/21 03:33:02 GMT
FROM:    Sibasish Laha at GSFC  <sibasish.laha@nasa.gov>

T. Sakamoto (AGU), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-60 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210419C (trigger #1044236)
(Moss et al., GCN Circ. 29834).  The BAT ground-calculated position is
RA, Dec = 212.969, 36.011 deg which is
   RA(J2000)  =  14h 11m 52.6s
   Dec(J2000) = +36d 00' 40.5"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 72%.

The BAT light curve showed a complex structure with a duration of about ~70 sec.
T90 (15-350 keV) is 73.00 +- 16.40 sec (estimated error including systematics).

The time-averaged spectrum from T+16.00 to T+102.00 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.50 +- 0.27.  The fluence in the 15-150 keV band is 8.1 +- 1.2 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T+48.00 sec in the 15-150 keV band
is 0.8 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1044236/BA/


GRB_name: GRB210421A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29857
SUBJECT: GRB 210421A: DDOTI Upper Limit
DATE:    21/04/21 04:56:00 GMT
FROM:    Alan M Watson at UNAM  <alan@astro.unam.mx>

Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), Simone Dichiara
(GSFC/UMD), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), OcÃ©lotl Lopez
(UNAM), Diego Gonzalez (UNAM), Margarita Pereyra (UNAM), Srihari Ravi (ASU), and
Eleonora Troja (GSFC/UMD) report:

We observed the field of the Swift/BAT GRB 210421A (Moss et al., GCN Circ.
29849) with the DDOTI wide-field imager at the Observatorio AstronÃ³mico Nacional
on Sierra San Pedro Martir (http://ddoti.astroscu.unam.mx) from 2021-04-21 03:05
to 04:33 UTC (from 2.6 to 4.1 hours after the trigger) and obtained 4320 seconds
of exposure in the w filter.

We observed a region covering aproximately 7 degrees in RA and 10 degrees in
declination (about 70 square degrees), including the XRT position. We calibrated
our images against the APASS catalog.

We do not detect any source in the XRT region to a 3-sigma limiting AB magnitude of
w = 21.1.

We thank the staff of the Observatorio Astronomico Nacional in San Pedro Martir.


GRB_name: GRB210420B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29858
SUBJECT: GRB 210420B: DDOTI Detection of the Afterglow
DATE:    21/04/21 09:15:45 GMT
FROM:    Alan M Watson at UNAM  <alan@astro.unam.mx>

Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), Simone Dichiara
(GSFC/UMD), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), OcÃ©lotl Lopez
(UNAM), Diego Gonzalez (UNAM), Margarita Pereyra (UNAM), Srihari Ravi (ASU), and
Eleonora Troja (GSFC/UMD) report:

We observed the field of the Swift/BAT GRB 210420B (Moss et al., GCN Circ.
29844) with the DDOTI wide-field imager at the Observatorio AstronÃ³mico Nacional
on Sierra San Pedro Martir (http://ddoti.astroscu.unam.mx) from 2021-04-21 04:36
to 08:15 UTC (from 10.0 to 13.7 hours after the trigger) and obtained 10380
seconds of exposure in the w filter.

We observed a region covering aproximately 7 degrees in RA and 10 degrees in
declination (about 70 square degrees), including the XRT position. We calibrated
our images against the APASS catalog.

We detect a source at 16:57:17.97 +42:34:12.3 J2000 with an AB magnitude of w =
21.47 +/- 0.09.

This source is outside the XRT error region reported by Moss et al. (GCN Circ.
29844), but is not present in the Pan-STARRS DR1 g image of the field and is
consistent with the afterglow coordinates reported by Oksanen (GCN Circ. 29846),
Lipunov et al. (GCN Circ. 29845), Leonini et al. (GCN Circ. 29851), and de
Ugarte Postigo et al. (GCN Circ. 29852).

We thank the staff of the Observatorio Astronomico Nacional in San Pedro Martir.


GRB_name: GRB210419C
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29859
SUBJECT: GRB 210419C: MITSuME Akeno optical upper limits
DATE:    21/04/21 09:18:53 GMT
FROM:    Katsuhiro L. Murata at Nagoya U  <murata@u.phys.nagoya-u.ac.jp>

K. L. Murata, R. Hosokawa, M. Niwano, N. Ito, H. Takamatsu, Y. Yatsu, and
N.Kawai (TokyoTech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 210419C (M. J. Moss et al. GCN Circular
#29834, A.P. Beardmore et al. GCN Circular #29839, WeiKang Zheng and Alexei
V. Filippenko report on et al. GCN Circular #29840, Simone Leonini et al.
GCN Circular #29842, Nat Butler et al. GCN Circular #29843, T. Sakamoto et
al. GCN Circular #29856) with the optical three color (g', Rc, and Ic) CCD
cameras attached to the MITSuME 50 cm telescope of Akeno Observatory,
Yamanashi, Japan. The observation with a series of 60 sec exposures started
at 2021-04-20 10:40:08 UT (11.2 hours after the Swift BAT trigger). We
stacked the images with good conditions. We did not detect any sources
within the enhanced XRT error region (A.P. Beardmore et al. GCN Circular
#29839) in all three bands. We obtained the 5-sigma limits of the stacked
images as follows.

T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
11.6 11:38 3000 g'>19.6, Rc>19.9, Ic>19.3
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used the PS1 catalog for flux calibration.
The magnitudes are expressed in the AB system.
The images were processed in real-time through the MITSuME GPU reduction
pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1, Pages 4-24;
https://github.com/MNiwano/Eclaire).


GRB_name: GRB210413B
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29860
SUBJECT: GRB 210413B: MITSuME Okayama optical upper limits
DATE:    21/04/21 09:41:19 GMT
FROM:    Naohiro Ito at Tokyo Tech  <n.ito@hp.phys.titech.ac.jp>

N. Ito, K. L. Murata, R. Hosokawa, M. Niwano, H. Takamatsu, Y. Yatsu,
and N.Kawai (TokyoTech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 210413B (Fermi/GBM TRIGGER 640050417, P.
A. Evans et al. GCN Circular #29821, Gregory S.H. Paek et al. GCN
Circular #29825, J.A. Kennea et al. GCN Circular #29827) with the
optical three color (g', Rc, and Ic) CCD cameras attached to the
MITSuME 50 cm telescope of Okayama Astronomical Observatory, Okayama,
Japan. The observation with a series of 60 sec exposures started at
2021-04-17 13:31:10 UT (85.8 hours after the Fermi/GBM trigger
640050417). We stacked the images with good conditions. We did not
find any transients within the BAT error region (A. Tohuvavohu et al.
GCN Circular #29819) in all three bands. We obtained the 5-sigma
limits of the stacked images as follows.

T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
86.8 15:06 2340 g'>17.4, Rc>17.6, Ic>17.3
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used the PS1 catalog for flux calibration.
The magnitudes are expressed in the AB system.
The images were processed in real-time through the MITSuME GPU
reduction pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1, Pages
4-24; https://github.com/MNiwano/Eclaire).


GRB_name: GRB210420B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29861
SUBJECT: GRB 210420B: KAIT Optical Observations
DATE:    21/04/21 14:39:40 GMT
FROM:    Weikang Zheng at UC Berkeley  <weikang@berkeley.edu>

WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on

behalf of the KAIT GRB team:


The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at

Lick Observatory, responded to the Swift GRB 210420B (Moss et al.,

GCN 29844) starting at ~0.61 days after the Swift trigger (Lien et al.

GCN 29854). A total of 30x60s images were obtained in the clear (roughly R)

filters. We detect the optical afterglow (Lipunov et al., GCN 29845;
Oksanen,

GCN 29846; Hu et al., GCN 29847; Sun et al., GCN 29848; Leonini et al.,

GCN 29851; de Ugarte Postigo et al., GCN 29852; Watson et al., GCN 29858)

in the coadd image with a mag of 19.9 +/- 0.2, calibrated to the

Pan-STARRS1 catalog.


GRB_name: GRB210420B
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29862
SUBJECT: GRB 210420B: Swift/UVOT Detection
DATE:    21/04/21 14:42:18 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and M. J. Moss (GWU) report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210420B 147s after the BAT trigger 
(Moss et al., GCN Circ. 29844 and updated in Lien et al., GCN Circ. 29854).
A fading source consistent with the optical counterpart reported by Lipunov et al. GCN Circ. 29845, 
Oksanen GCN Circ. 29846, Hu et al. GCN Circ. 29847, Tianrui et al. GCN Circ. 29848, Leonini et al. 
GCN Circ. 29851, de Ugarte Postigo et al. GCN Circ. 29852 and Watson et al. GCN Circ. 29858, is 
detected in the initial UVOT exposures.

Preliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 
1358, 373) for the first finding chart (_fc) exposure and other early exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

u_fc               147          391          240         16.2 Â± 0.04
u                18793        19317          512         18.6 Â± 0.1
v                  447          467           20         16.7 Â± 0.2
b                  397          417           19         17.1 Â± 0.1
w1                 496          516           20         16.5 Â± 0.2
m2                 620         1121           39         17.2 Â± 0.2
w2                1201         1371           39         17.6 Â± 0.2

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of 
E(B-V) = 0.022 in the direction of the burst (Schlegel et al. 1998).


GRB_name: GRB210420B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29863
SUBJECT: GRB 210420B: Tautenburg observations 
DATE:    21/04/21 15:01:05 GMT
FROM:    Sylvio Klose at TLS Tautenburg  <klose@tls-tautenburg.de>

B. Stecklum, A. Nicuesa Guelbenzu, S. Klose, S. Melnikov, and U. Laux
(all Tautenburg) report:

We observed the field of GRB 210420B (Moss et al., GCN 29844) with the 
Tautenburg 1.34m Schmidt telescope equipped with the TAUKAM 6k x 6k CCD 
camera. Observations started on April 20 at 20:13:21 UT, 99 min after the 
BAT trigger (Lien et al., GCN 29854). Altogether four observing runs (5x5 
min each) were performed (Sloan r'). The afterglow (Lipunov et al., GCN 
29845; Oksanen, GCN 29846; Hu et al., GCN 29847; Sun et al., GCN 29848; 
Leonini et al., GCN 29851; de Ugarte Postigo et al., GCNs 29852, 29853; 
Watson et al., GCN 29858) was clearly detected in all frames. Magnitudes 
were calibrated against SDSS.

The data show that between the first (mean time: 20:26:10 UT; r' = 18.30 
+/- 0.03) and the second observing run (mean time: 21:47:07 UT; r' = 18.75 
+/- 0.03) ) the light curve was steepening to a decay with alpha2 = 0.99 
+/- 0.04 (break time tb = 0.091 +/- 0.017 days). Before the break the 
decay index is not well constrained (alpha1 = 0.35 +/- 0.33).


GRB_name: GRB210420B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29864
SUBJECT: GRB 210420B: RATIR Optical and NIR Observations
DATE:    21/04/21 15:03:09 GMT
FROM:    Nat Butler at Az State U  <natbutler@asu.edu>

Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William
H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier
Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora
Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), JesÃºs
GonzÃ¡lez (UNAM), Carlos RomÃ¡n-ZÃºÃ±iga (UNAM), Harvey Moseley (GSFC), John
Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report:

We observed the field of GRB 210420B (Moss, et al., GCN 29844) with the
Reionization and Transients Infrared Camera (RATIR) on the 1.5m Harold
Johnson Telescope at the Observatorio AstronÃ³mico Nacional on Sierra San
Pedro MÃ¡rtir from 2021/04 21.39 to 2021/04 21.49 UTC (13.73 to 16.08 hours
after the BAT trigger), obtaining a total of 1.47 hours exposure in the r
and i bands and 0.55 hours exposure in the Z, Y, J, and H bands.

We detect the source reported by Oksanen (GCN 29846), Lipunov et al. (GCN
29845), Leonini et al. (GCN 29851), de Ugarte Postigo et al. (GCN 29852),
Watson et al. (GCN 29858), Zheng et al. (GCN 29861), and Breeveld et al.
(GCN 29862).  In comparison with the SDSS DR9 and 2MASS catalogs, we obtain:

  r = 19.98 +/- 0.02
  i = 19.77 +/- 0.02
  Z = 19.70 +/- 0.03
  Y = 19.48 +/- 0.05
  J = 19.31 +/- 0.05
  H = 19.26 +/- 0.08

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.

We thank the staff of the Observatorio AstronÃ³mico Nacional in San Pedro
MÃ¡rtir.


GRB_name: GRB210421A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29865
SUBJECT: GRB 210421A: Enhanced Swift-XRT position
DATE:    21/04/21 15:22:26 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1675 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 210421A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 104.87443, +4.92232 which is equivalent
to:

RA (J2000): 06h 59m 29.86s
Dec (J2000): +04d 55' 20.4"

with an uncertainty of 2.4 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB210420B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29866
SUBJECT: GRB 210420B: Ondrejov D50 optical afterglow detection
DATE:    21/04/21 15:32:16 GMT
FROM:    Martin Jelinek at Astro.Inst-AVCR,Ondrejov  <martin.jelinek@asu.cas.cz>

M. Jelinek, J. Strobl, R. Hudec, C. Polasek (ASU CAS Ondrejov)

report:

We observed the position of the bright GRB 210420B (Moss et al., GCN 29833
& Lien et al., GCN 29854) with the D50 telescope of the Astronomical
Institute Ondrejov, near Prague, Czech  Republic. We performed a series of
120 s unfiltered exposures starting 21:10 UT, between 2.6 and 4.9 h after
the trigger.

The optical afterglow (Lipunov et al., GCNC 29845; Oksanen et al., GCNC
29846; Hu et al., GCNC 29847; Tianrui Sun et al., GCNC 29848; Leonini et
al., GCNC 29851; de Ugarte Postigo et al., GCNC 29852; de Ugarte Postigo et
al., GCNC 29853; Watson et al., GCNC 29858; Zheng et al., GCNC 29861;
Breeveld et al., GCNC 29862; Stecklum et al., GCNC 29863 and Butler et al.,
GCNC 29864) is clearly detected in single 120 s images, at least at the
beginning of the series.

We can confirm a decaying nature of the object - the afterglow faded > 0.4
mag during the course of our observations, providing an alpha decay of 0.69
+- 0.17.


GRB_name: GRB210420B
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29867
SUBJECT: GRB 210420B: Correction to DDOTI Magnitude 
DATE:    21/04/21 15:58:43 GMT
FROM:    Alan M Watson at UNAM  <alan@astro.unam.mx>

There was a transcription error in the DDOTI magnitude reported by Watson et al.
(GCN Circ. 29858) for GRB 210420B. The correct magnitude is w = 20.47 +/- 0.09.


GRB_name: GRB210419C
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29868
SUBJECT: GRB 210419C: Swift/UVOT Upper Limits
DATE:    21/04/21 16:30:59 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M. H. Siegel (PSU) and M. J. Moss (GWU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210419C
156 s after the BAT trigger (Moss et al., GCN Circ. 29834).
No optical afterglow consistent with the XRT position
(Beardmore et al. GCN Circ. 29839)
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           156          305          147         >20.83
white             6954        17801          254         >21.14
v                11428        28719          155         >19.22
b                 6749        17713         1081         >21.37
u                  313          408           93         >19.55
u                 6544        22974          258         >20.20
UVW1              6339        22905         1082         >20.49
UVM2              6134         6334          196         >19.21
UVW2             10522        28626         1771         >20.84

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.010 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210421B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29870
SUBJECT: GRB 210421B: Fermi GBM Final Localization
DATE:    21/04/21 20:03:10 GMT
FROM:    Joe Mangan at UCD  <joseph.mangan@ucdconnect.ie>

The Fermi GBM team reports the detection of a likely short GRB

At 10:54:44.812 UT on 21 Apr 2021, the Fermi Gamma-ray Burst Monitor
(GBM) triggered and located GRB 210421B (trigger 640695289 /
210421455).

The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 272.1, Dec = 57.2(J2000 degrees, equivalent to J2000 18h 08m,
57d 09'), with a statistical uncertainty of 2.1 degrees.

The angle from the Fermi LAT boresight is 20.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210421455/quicklook/glg_skymap_all_bn210421455.png

The HEALPix FITS file, including the estimated localization
systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210421455/quicklook/glg_healpix_all_bn210421455.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210421455/quicklook/glg_lc_medres34_bn210421455.gif


GRB_name: GRB210421C
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29871
SUBJECT: GRB 210421C: Fermi GBM Final Real-time Localization
DATE:    21/04/21 20:23:17 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely SHORT GRB

At 20:12:53 UT on 21 Apr 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210421C (trigger 640728778.025922 / 210421842).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 192.2, Dec = -61.9 (J2000 degrees, equivalent to J2000 12h 48m, -61d 53'), with a statistical uncertainty of 14.3 degrees.

The angle from the Fermi LAT boresight is 125.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210421842/quicklook/glg_skymap_all_bn210421842.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210421842/quicklook/glg_healpix_all_bn210421842.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210421842/quicklook/glg_lc_medres34_bn210421842.gif


GRB_name: GRB210420B
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29872
SUBJECT: GRB 210420B: Montarrenti Observatory follow-up observations
DATE:    21/04/21 21:17:34 GMT
FROM:    Simone Leonini at Monarrenti Obs  <s.leonini@iol.it>

Simone Leonini, M. Conti, P. Rosi and L.M. Tinjaca Ramirez (Montarrenti Observatory, Siena, Italy) report:

In reference to the GRB 210420B (Moss, et al., GCN 29844), as a follow-up of our early observations already reported in GCN 29851, we kept on imaging the afterglow until 2021-04-21 02:49:13 UT with the same conditions, set-up and analysis. Here our complete set of measurements:

2021 Apr 20.99207 UT (23:48:35 mid-time) R=19.0 +/-0.13
2021 Apr 21.03089 UT (00:44:29 mid-time) R=19.2 +/-0.14
2021 Apr 21.06793 UT (01:37:49 mid-time) R=19.1 +/-0.14
2021 Apr 21.11587 UT (02:46:51 mid-time) R=19.5 +/-0.12

Along the span of our observations we estimate from our measurements a decay rate of 1.02+/-0.35.


GRB_name: GRB210421C
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29873
SUBJECT: Fermi GRB 210421C: Global MASTER-Net observations report 
DATE:    21/04/21 21:30:14 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-SAAO robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 210421C ( Fermi GBM team, GCN 29871) errorbox  3606 sec after notice time and 3636 sec after trigger time at 2021-04-21 21:13:29 UT, with upper limit up to  18.8 mag. The observations began at zenith distance = 24 deg. The sun  altitude  is -62.3 deg. 

The galactic latitude b =  1 deg., longitude l = 303 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1598370

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

    3666 | 2021-04-21 21:13:29 |         MASTER-SAAO | (12h 44m 20.32s , -55d 59m 18.1s) |   C |    60 | 18.5 |        
    3839 | 2021-04-21 21:16:21 |         MASTER-SAAO | (13h 00m 06.56s , -55d 58m 20.2s) |   C |    60 | 17.6 |        
    3918 | 2021-04-21 21:17:41 |         MASTER-SAAO | (12h 35m 41.98s , -53d 57m 24.5s) |   C |    60 | 18.4 |        
    4248 | 2021-04-21 21:23:10 |         MASTER-SAAO | (12h 47m 33.26s , -53d 57m 52.4s) |   C |    60 | 18.8 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210421B
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29874
SUBJECT: GRB 210421B: Correction of GRB Type to "Likely Long GRB"
DATE:    21/04/21 21:45:35 GMT
FROM:    Joe Mangan at UCD  <joseph.mangan@ucdconnect.ie>

Correction to GCN Circ. 29870 for GRB 210421B, GRB type originally reported
as "likely short GRB", corrected to "likely long GRB".


GRB_name: GRB210421A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29875
SUBJECT: GRB 210421A: Swift-XRT refined Analysis
DATE:    21/04/21 22:39:46 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), E. Ambrosi 
(INAF-IASFPA) , M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR),
D.N. Burrows (PSU), J. D. Gropp (PSU), J.A. Kennea (PSU), K.L. Page (U.
Leicester) and M.J. Moss report on behalf of the Swift-XRT team:

We have analysed 6.4 ks of XRT data for GRB 210421A (Moss et al. GCN
Circ. 29849), from 91 s to 68.9 ks after the  BAT trigger. The data
comprise 130 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Evans et al. (GCN Circ. 29865).

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=2.6 (+0.8, -0.9). At T+109 s  the decay
steepens to an alpha of 4.96 (+0.17, -0.15) before breaking again at
T+397 s to a final decay with index alpha=0.59 (+0.22, -0.14).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.74 (+/-0.08). The
best-fitting absorption column is  5.3 (+/-0.3) x 10^21 cm^-2, in
excess of the Galactic value of 4.6 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.17 (+0.19, -0.14)
and a best-fitting absorption column consistent with the Galactic
value. The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 3.7 x 10^-11 (6.5 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      4.6 (+0.8, -0.0) x 10^21 cm^-2
Galactic foreground: 4.6 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:      2.17 (+0.19, -0.14)

If the light curve continues to decay with a power-law decay index of
0.59, the count rate at T+24 hours will be 0.011 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.1 x
10^-13 (7.4 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01044426.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210420B
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29876
SUBJECT: GRB 210420B: Swift-XRT refined Analysis
DATE:    21/04/21 22:44:06 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

J.P. Osborne (U. Leicester), M. Capalbi (INAF-IASFPA), M. Perri (SSDC &
INAF-OAR), V. D'Elia (SSDC & INAF-OAR), J. D. Gropp (PSU), J.A. Kennea
(PSU), A. Tohuvavohu (U. Toronto), K.L. Page (U. Leicester), A.P.
Beardmore (U. Leicester) and M.J. Moss report on behalf of the
Swift-XRT team:

We have analysed 4.8 ks of XRT data for GRB 210420B (Moss et al. GCN
Circ. 29844), from 141 s to 87.5 ks after the  BAT trigger. The data
comprise 177 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The refined XRT position is RA, Dec =
254.3227, +42.5696 which is equivalent to:

RA (J2000): 16 57 17.45
Dec(J2000): +42 34 10.6

with an uncertainty of 3.5 arcsec (radius, 90% confidence).

The light curve can be modelled with an initial power-law decay with an
index of alpha=2.23 (+0.11, -0.12), followed by a break at T+425 s to
an alpha of 1.13 (+/-0.07).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.72 (+0.08, -0.07). The
best-fitting absorption column is  9 (+11, -9) x 10^20 cm^-2, at a
redshift of 1.4, in addition to the Galactic value of 2.1 x 10^20 cm^-2
(Willingale et al. 2013). The PC mode spectrum has a photon index of
1.61 (+0.08, -0.07) and a best-fitting absorption column consistent
with the Galactic value. The counts to observed (unabsorbed) 0.3-10 keV
flux conversion factor deduced from this spectrum  is 4.0 x 10^-11 (4.2
x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Galactic foreground: 2.1 x 10^20 cm^-2
Intrinsic column:    2.1 (+6.0, -0.0) x 10^20 cm^-2 at z=1.4
Photon index:      1.61 (+0.08, -0.07)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01044382.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210421B
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29877
SUBJECT: GRB 210421B: Swift/BAT-GUANO detection and arcminute localization
DATE:    21/04/21 22:47:22 GMT
FROM:    Aaron Tohuvavohu at U Toronto  <aaron.tohu@gmail.com>

James DeLaunay (PSU), Aaron Tohuvavohu (U Toronto), Jamie A. Kennea
(PSU) report:

Swift/BAT did not trigger on GRB 210421B (T0: 2021-04-21 10:54:44 UTC,
Fermi/GBM GCN 29870, 29874; INTEGRAL/SPI-ACS trigger 9154).

The INTEGRAL/SPI-ACS notice, distributed in near real-time triggered
the Swift Mission Operations Center operated Gamma-ray Urgent Archiver
for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).

Upon trigger by this notice, GUANO sent a command to the Swift Burst
Alert Telescope (BAT) to save 90 seconds of BAT event-mode data from
[-45,+45] seconds around the time of the burst. All the requested
event mode data was delivered to the ground.

The burst is strongly detected in BAT with a duration of ~15 seconds,
confirming the long classification correction of Fermi/GBM (GCN
29874).
The burst occurred during a Swift slew.
The position of the burst was found with SNR of 9.7 using a novel slew
image mosaicing procedure (DeLaunay et al. 2021, in prep.), and so the
positional uncertainty is not yet well characterized.

The BAT position is
RA, Dec = 270.817, 56.828 deg which is
   RA(J2000)  = 18h 03m 16.08s
   Dec(J2000) =  56d 49â€™ 40.8â€
with an estimated uncertainty of at least 5 arcmin.

This position is consistent with the Fermi GBM localization (GCN 29870).

XRT and UVOT follow-up has been requested. Results of follow-up
observations will be reported in future circulars.

GUANO is a fully autonomous, extremely low latency, spacecraft
commanding pipeline designed for targeted recovery of BAT event mode
data around the times of compelling astrophysical events to enable
more sensitive GRB searches.

A live reporting of Swift/BAT event data recovered by GUANO can be
found at: https://www.swift.psu.edu/guano/


GRB_name: GRB210421B
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29878
SUBJECT: GRB 210421B: Swift ToO observations
DATE:    21/04/22 01:26:20 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a ToO observation of the Swift/BAT GRB 210421B. 
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021429

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Swift/BAT event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a 
GCN Circular after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210420B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29879
SUBJECT: GRB 210420B: Swift-BAT refined analysis
DATE:    21/04/22 02:14:37 GMT
FROM:    Sibasish Laha at GSFC  <sibasish.laha@nasa.gov>

M. Stamatikos (OSU), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-239 to T+767 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210420B (trigger #1044382)
(Moss et al., GCN Circ. 29844).  The BAT ground-calculated position is
RA, Dec = 254.313, 42.558 deg which is
   RA(J2000)  =  16h 57m 15.1s
   Dec(J2000) = +42d 33' 28.1"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 77%.

The BAT light curve showed a complex structure with a duration of about ~160 sec.
T90 (15-350 keV) is 158.8 +- 29.5 sec (estimated error including systematics).

The time-averaged spectrum from T-21.30 to T+160.09 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.49 +- 0.19.  The fluence in the 15-150 keV band is 1.5 +- 0.2 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+21.02 sec in the 15-150 keV band
is 0.5 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1044382/BA/


GRB_name: GRB210419B
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29881
SUBJECT: GRB 210419B: AstroSat CZTI detection
DATE:    21/04/22 10:55:41 GMT
FROM:    Varun Bhalerao at Indian Inst of Tech  <varunb@iitb.ac.in>

P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), S. Gupta (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:

Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al, 2020, arxiv:2011.07067) showed detection of a long GRB 210419B, which was also detected by Fermi-GBM (GCN #29831).

It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed a broad emission peak with the strongest peak at 2021-04-19 21:10:25.625 UT. The measured peak count rate is 1623 (+4 ,-4) cts/s above the background in the combined Veto data of four quadrants, with a total of 3054 (+641, -726) cts. The local mean background count rate was 181 (+89, --3) cts/s. We measure a T90 of 35 (+9, -12) s from the cumulative Veto light curve.

CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project


GRB_name: GRB210421A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29882
SUBJECT: GRB 210421A: MITSuME Akeno optical upper limits
DATE:    21/04/22 14:52:20 GMT
FROM:    Naohiro Ito at Tokyo Tech  <n.ito@hp.phys.titech.ac.jp>

N. Ito, K. L. Murata, R. Hosokawa, M. Niwano, H. Takamatsu, Y. Yatsu,
and N.Kawai (TokyoTech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 210421A (M. J. Moss et al. GCN Circular
#29849, V. Lipunov et al. GCN Circular #29850, Alan M. Watson et al.
GCN Circular #29857, P.A. Evans et al. GCN Circular #29865, P.A. Evans
et al. GCN Circular #29875) with the optical three color (g', Rc, and
Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno
Observatory, Yamanashi, Japan. The observation with a series of 60 sec
exposures started at 2021-04-21 09:51:58 UT (9.4 hours after the Swift
BAT trigger) We stacked the images with good conditions. We did not
detect any sources within the enhanced XRT error region (P.A. Evans et
al. GCN Circular #29865) in all three bands.
We obtained the 5-sigma limits of the stacked images as follows.

T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
9.8 11:25 7020 g'>18.8, Rc>18.8, Ic>18.4
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used the PS1 catalog for flux calibration.
The magnitudes are expressed in the AB system.
The images were processed in real-time through the MITSuME GPU
reduction pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1, Pages
4-24; https://github.com/MNiwano/Eclaire).


GRB_name: GRB210420B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29883
SUBJECT: GRB 210420B: follow-up photometry of the optical afterglow at Konkoly
DATE:    21/04/22 17:53:17 GMT
FROM:    Jozsef Vinko at Konkoly Observator  <vinko@konkoly.hu>

J. Vinko (Konkoly/ELTE/U Szeged), L. Kriskovics, R. Szakats, A. Pal and K. Vida (Konkoly)
report on behalf of the "Transient Astrophyical Objects" project:

We observed the field of GRB 210420B (Moss et al., GCN 29833; Lien et al., GCN 29854; 
Osborne et al. GCN 29876; Stamatikos et al., GCN29879) with the 0.8m RC80 robotic telescope at Piszkesteto Mountain Station of Konkoly Observatory through SDSS r' and i' filters on 
2021 Apr 21.85 UT (MJD 59325.85, 1.07 day after the trigger). The total exposure time 
was 1800 s in both filters. 

The frames were tied to PS1-photometry of local stellar sources. We detect the optical 
afterglow (Lipunov et al., GCN 29845; Oksanen et al., GCN 29846; Hu et al., GCN 29847;
Tianrui Sun et al., GCN 29848; Leonini et al., GCN 29851; de Ugarte Postigo et al., 
GCN 29852, 29853; Watson et al., GCN 29858; Zheng et al., GCN 29861; Breeveld et al., 
GCN 29862; Stecklum et al., GCN 29863; Butler et al.,GCN 29864; Jelinek et al., GCN 29866;
Watson, GCN 29867; Leonini et al., GCN 29872) is detected on the stacked r-band images. 
Forced photometry at the position of the GRB, tied to the PS1 photometry of nearby stars, 
resulted in the following AB-magnitudes:

r = 20.76 +/- 0.33 (5-sigma limit 22.18)
i > 22.09 (5-sigma limit)


GRB_name: GRB210420B
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29884
SUBJECT: GRB 210420B: Correction to AST3-3 YaoAn magnitude
DATE:    21/04/22 18:48:15 GMT
FROM:    Tianrui Sun at Purple Mountain Obs,CAS  <trsun@pmo.ac.cn>

There was a program error to the AST3-3 YaoAn observation:
The two magnitudes reported by Tianrui Sun et al.(GCNC 29848) for GRB 210420B contain an error.
Thus, the correct description should be: 
The detected candidate source in g-band was 18.6 mag +/- 0.06 at 2021-04-20T20:07:30.596 and 19.13 mag +/- 0.1 mag at 2021-04-20T21:42:43.897.


GRB_name: GRB210421A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29885
SUBJECT: GRB 210421A: Swift/UVOT Upper Limits
DATE:    21/04/22 18:53:07 GMT
FROM:    Samantha Oates at MSSL  <samantha.oates@alumni.ucl.ac.uk>

S. R. Oates (U.Birmingham) and M. J. Moss (GWU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210421A
96 s after the BAT trigger (Moss et al., GCN Circ. 29849).
No optical afterglow consistent with the XRT position
(Evans et al., GCN Circ. 29865).
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC              96           246          147         >20.4
white                96          1912          191         >20.6
v                1608          1800           39         >17.9
b                1534          1899           58         >19.2
u_FC                  308           484          173         >19.5
u                  308          1874          211         >19.6
uvw1             1658          1850           39         >18.1
uvm2             1633          1825           39         >17.9
uvw2             1584          1776           39         >18.3

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.318 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210422A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29886
SUBJECT: GRB 210422A: Swift detection of a burst
DATE:    21/04/22 23:07:53 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

E. Troja (NASA/GSFC/UMCP), C. Gronwall (PSU), A. Y. Lien (GSFC/UMBC)
and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels
Swift Observatory Team:

At 17:47:10 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210422A (trigger=1044678). Due to an observing constraint,
Swift did not slew immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 21.139, +42.110 which is 
   RA(J2000) = 01h 24m 33s
   Dec(J2000) = +42d 06' 36"
with an uncertainty of 3 arcmin (radius, 90% containment, 
including systematic uncertainty). The BAT light curve showed a 
single pulse structure with a duration of about 5 sec.  
The peak count rate was ~1000 counts/sec (15-350 keV), 
at ~0 sec after the trigger. 

Due to a Sun observing constraint, Swift cannot slew to the BAT 
position until 2021 June 4. There will thus be no XRT or UVOT data
for this trigger before this time. 

Burst Advocate for this burst is E. Troja (eleonora.troja AT nasa.gov). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB210421B
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29888
SUBJECT: GRB 210421B: AstroSat CZTI detection
DATE:    21/04/23 06:09:12 GMT
FROM:    Dipankar Bhattacharya at IUCAA  <dipankar@iucaa.in>

P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), S. Gupta (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: 



Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al, 2020, arxiv:2011.07067) showed detection of a long GRB 210421B, which was also detected by Fermi-GBM (GCN #29870) and Swift-BAT (GCN #29877). 


The source was clearly detected in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2021-04-21 10:54:43.5 UT. The measured peak count rate associated with the burst is 165 (+42, -33) cts/s above the background in the combined data of four quadrants, with a total of 905 (+230, -297) cts. The local mean background count rate was 504 (+4, -3) cts/s. Using cumulative rates, we measure a T90 of 16 (+3, -10) s. 


It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2021-04-21 10:54:43.6 UT. The measured peak count rate is 320 (+72, -54) cts/s above the background in the combined Veto data of four quadrants, with a total of 1481 (+436, -479) cts. The local mean background count rate was 1629 (+5, -6) cts/s. We measure a T90 of 17 (+4, -11) s from the cumulative Veto light curve. 


CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project. 


GRB_name: GRB210421A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29889
SUBJECT: GRB 210421A: GECAM detection
DATE:    21/04/23 06:37:40 GMT
FROM:    QiBin Yi at IHEP, HXMT  <yiqb@ihep.ac.cn>

S. L. Xie, X. Y. Song, Q. B. Yi, X. Y. Zhao, Y. Huang, S. L. Xiong,
S. Xiao, C. Cai, Y. Zhao, J. C. Liu, Y. Q. Zhang, W. C. Xue, C. Zheng,
Z. W. Guo, C. W. Wang, D. Y. Guo, P. Wang, X. B. Li, W. X. Peng, R. Qiao,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, J. J. He,
B. Li, C. Li, C. Y. Li, J. H. Li, Q. X. Li, X. Q. Li, Y. G. Li, X. H. Liang,
J. Y. Liao, J. C. Liu, X. J. Liu, Y. Q. Liu, F. J. Lu, Q. Luo, X. Ma,
G. Ou,  D. L. Shi, J. Y. Shi, L. M. Song, G. X. Sun, X. L. Sun, Y. L. Tuo,
J. Z. Wang, X. Y. Wen, Y. B. Xu, Y. P. Xu, S. Yang, M. Yao, B. X. Zhang,
C. Y. Zhang, D. L. Zhang, Fan Zhang, Fei Zhang, H. M. Zhang, K. Zhang,
P. Zhang, S. N. Zhang, Z. Zhang, S. Y. Zhao, S. J. Zheng, X. Zhou (IHEP),
report on behalf of GECAM team:

During the commissioning phase, GECAM-B triggered a long burst,
GRB 210421A, at 2021-04-21T00:27:32.000 UTC (denoted as T0),
which was also detected by Swift/BAT(GCN #29849). 

According to the GECAM-B light curves in about 8 keV - 115 keV, 
this burst mainly consists of multiple pulses with duration of about 20 s.

Although in-flight calibration has not been finalized yet, 
GECAM-B localized this burst to the following position (J2000):
Ra: 103.56 deg 
Dec: 2.26 deg 
Err: 3.46 deg (1-sigma,statistical only) 

The current systematic error of location is estimated to be several degrees
which could be minimized by the ongoing calibration. 

GECAM location is consistent with the Swift/BAT(GCN #29849) position
within the error.

The GECAM light curve could be found here: 
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/multiLCvsE_2021-04-21T003A273A32.950_.pdf

Please note that all GECAM results here are preliminary. The final analysis
will be published in journal papers or GECAM online catalog.

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in
Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time),
which was funded by the Chinese Academy of Sciences (CAS).


GRB_name: GRB210420B
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29890
SUBJECT: GRB 210420B: continued Tautenburg observations
DATE:    21/04/23 10:03:42 GMT
FROM:    Sylvio Klose at TLS Tautenburg  <klose@tls-tautenburg.de>

A. Nicuesa Guelbenzu, S. Klose, S. Melnikov, B. Stecklum, and U. Laux (all 
Tautenburg) report:

We continued observing the afterglow of GRB 210420B (Moss et al., GCN 
29844) with the Tautenburg 1.34m Schmidt telescope equipped with the 
TAUKAM 6k x 6k CCD camera.

Results are:

- run 2: midtime 01:35 UT, April 22: r' = 21.40 +/- 0.20 mag
- run 3: midtime 23:24 UT, April 22: r' > 22.7  (3 sigma)

Magnitudes were calibrated against SDSS stars in the field.

Our data (see Stecklum et al., GCN 29863) imply that between the 2nd and 
the 3rd observing run the decay of the light curve has steepened from 
alpha = 0.99 +/- 0.04 to alpha = 2.3 +/- 0.9, with a break time at 1.14 
+/- 0.29 days. Probably this is the classical jet break time. No further 
observations are planned.


GRB_name: GRB210421B
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29891
SUBJECT: GRB 210421B: AstroSat CZTI detection 
DATE:    21/04/23 12:44:05 GMT
FROM:    Varun Bhalerao at Indian Inst of Tech  <varunb@iitb.ac.in>

P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), S. Gupta (IITB), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:

Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al, 2020, arxiv:2011.07067) showed detection of a long GRB 210421B, which was also detected by Fermi-GBM (GCN #29870) and Swift (BAT - GCN #29877).

The source was clearly detected in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2021-04-21 10:54:43.5 UT. The measured peak count rate associated with the burst is 165 (+42, -33) cts/s above the background in the combined data of four quadrants, with a total of 905 (+230, -297) cts. The local mean background count rate was 504 (+4, -3) cts/s. Using cumulative rates, we measure a T90 of 16 (+3 -10) s. 

It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2021-04-21 10:54:43.647 UT. The measured peak count rate is 320 (+72, -54) cts/s above the background in the combined Veto data of four quadrants, with a total of 1481 (+436, -479) cts. The local mean background count rate was 1629 (+5, -6) cts/s. We measure a T90 of 17 (+4, -11) s from the cumulative Veto light curve.

CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.

Thanks,
Pallavi


GRB_name: GRB210421B
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29892
SUBJECT: GRB 210421B: Swift-XRT observations
DATE:    21/04/23 15:32:05 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), A. D'Ai
(INAF-IASFPA), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), B.
Sbarufatti (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U.
Leicester) and P.A. Evans (U. Leicester) report on behalf of the
Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Swift/BAT-detected burst GRB 210421B (James DeLaunay et al. GCN Circ.
29877), collecting 2.0 ks of Photon Counting (PC) mode data between
T0+45.1 ks and T0+85.2 ks. 

No X-ray sources have been detected. The 3-sigma upper limit in the
field ranges from ~0.004 to ~0.008 ct s^-1, corresponding to a 0.3-10
keV observed flux of 1.6e-13 to 3.4e-13 erg cm^-2 s^-1 (assuming a
typical GRB spectrum).

The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
https://www.swift.ac.uk/ToO_GRBs/00021429.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210421A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29893
SUBJECT: GRB 210421A: Swift-BAT refined analysis
DATE:    21/04/23 16:41:44 GMT
FROM:    Sibasish Laha at GSFC  <sibasish.laha@nasa.gov>

T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU),
(i.e. the Swift-BAT team):

Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210421A (trigger #1044426)
(Moss et al., GCN Circ. 29849).  The BAT ground-calculated position is
RA, Dec = 104.882, 4.928 deg which is
   RA(J2000)  =  06h 59m 31.7s
   Dec(J2000) = +04d 55' 41.2"
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 44%.

The BAT light curve showed a complex structure with a duration of about ~60 sec.
T90 (15-350 keV) is 79.52 +- 26.78 sec (estimated error including systematics).

The time-averaged spectrum from T-21.74 to T+73.22 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.10 +- 0.72,
and Epeak of 35.2 +- 8.5 keV (chi squared 61.93 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 2.0 +- 0.2 x 10^-06 erg/cm2
and the 1-sec peak flux measured from T+2.47 sec in the 15-150 keV band is
2.0 +- 0.3 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 2.10 +- 0.13 (chi squared 69.44 for 57 d.o.f.).  All the quoted errors
are at the 90% confidence level.

The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/BATbursts/1044426/bascript/top.html


GRB_name: GRB210420B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29894
SUBJECT: GRB 210420B: Zeiss-1000 of Koshka optical observations
DATE:    21/04/23 18:31:49 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

N. Pankov (HSE, IKI), S. Naroenkov (INASAN), A. Pozanenko (IKI),  S. 
Belkin (IKI), M. Ibrahimov (INASAN)  report  on behalf of IKI GRB FuN:

We observed the field of  GRB 210420B (Moss et al., GCN 29833; Lien et 
al., GCN 29854; Osborne et al. GCN 29876; Stamatikos et al., GCN29879) 
with Zeiss-1000 telescope of Koshka observatory (INASAN). We marginally 
detect the optical afterglow  (Lipunov et al., GCN 29845; Oksanen et 
al., GCN 29846; Hu et al., GCN 29847; Tianrui Sun et al., GCN 29848; 
Leonini et al., GCN 29851; de Ugarte Postigo et al., GCN 29852, 29853; 
Watson et al., GCN 29858; Zheng et al., GCN 29861; Breeveld et al., GCN 
29862; Stecklum et al., GCN 29863; Butler et al.,GCN 29864; Jelinek et 
al., GCN 29866; Watson, GCN 29867; Leonini et al., GCN 29872; Guelbenzu 
et al., GCN 29890).

Preliminary photometry of the afterglow is following

Date       UT start   t-T0       Filter Exp.    OT    Err.  UL(3sigma)
                      (mid, days)        (s)
2021-04-21  20:02:55    15*180    1.03507 R    21.0   0.3  21.0
2021-04-22  20:16:45    24*180    2.05405 R     n/d   n/d  20.5


The photometry is based on the nearby USNO-B1.0 stars
USNO_B1.0_id R2
1325-0345119 16.12
1326-0349499 16.57


GRB_name: GRB210420B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29895
SUBJECT: GRB 210420B: follow-up photometry of optical afterglow at INASAN/Simeiz
DATE:    21/04/24 12:33:31 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

M. Ibrahimov, S. Naroenkov, I. Nikolenko (all from INASAN, Moscow, Russia) and
O. Pons (IGA, Habana, Cuba) report on behalf of a larger team:

Using Zeiss 1m telescope and 4K FLI PL16803 CCD of Simeiz Obserbatory
(Collective Usage Center of INASAN), we observed the field of GRB 210420B
(Moss et al., GCN 29844; Lien et al., GCN 29854; Osborne et al. GCN 29876;
Stamatikos et al., GCN29879). 15x180sec images were acquired through Bessel R
filter on 2021-04-21/20:47:03 UT (midpoint time, 1.09 day after trigger) with
a total exposure time of 2700 sec.


Optical afterglow (Lipunov et al., GCN 29845; Oksanen et al., GCN 29846; Hu et
al., GCN 29847; Tianrui Sun et al., GCN 29848; Leonini et al., GCN 29851; de
Ugarte Postigo et al., GCN 29852, 29853; Watson et al., GCN 29858; Zheng et
al., GCN 29861; Breeveld et al., GCN 29862; Stecklum et al., GCN 29863; Butler
et al., GCN 29864; Jelinek et al., GCN 29866; Watson, GCN 29867; Leonini et
al., GCN 29872; Vinko et al., GCN 29883; Tianrui Sun, GCN 29884; Guelbenzu et
al., GCN 29890) was marginally detected on the stacked R image.


Photometry of the detected optical afterglow, calibrated against USNO-B1
photometry of nearby stars, resulted in: R = 21.8 +/- 0.5 mag.


Research was supported by Project No. RFMEFI61319X0093 (Russian Ministry of
Science and High Education, Agreement No. 075-15-2019-1716 by 2019 Nov 20) and
Project No. 19-29-11013 (Russian Foundation of Fundamental Investigation,
Agreement No. 19-29-11013\20 by 2021 Jan 21).

On behalf of M. Ibrahimov.


GRB_name: GRB210424A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29896
SUBJECT: GRB 210424A: Fermi GBM Final Real-time Localization
DATE:    21/04/24 18:50:18 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 18:40:11 UT on 24 Apr 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210424A (trigger 640982416.446996 / 210424778).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 9.0, Dec = 13.7 (J2000 degrees, equivalent to J2000 00h 36m, 13d 41'), with a statistical uncertainty of 14.1 degrees.

The angle from the Fermi LAT boresight is 72.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210424778/quicklook/glg_skymap_all_bn210424778.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210424778/quicklook/glg_healpix_all_bn210424778.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210424778/quicklook/glg_lc_medres34_bn210424778.gif


GRB_name: GRB210422A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29897
SUBJECT: GRB 210422A: Swift-BAT refined analysis
DATE:    21/04/25 00:00:01 GMT
FROM:    Sibasish Laha at GSFC  <sibasish.laha@nasa.gov>

S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210422A (trigger #1044678)
(Troja et al., GCN Circ. 29886).  The BAT ground-calculated position is
RA, Dec = 21.077, 42.100 deg which is
   RA(J2000)  =  01h 24m 18.6s
   Dec(J2000) = +42d 05' 58.2"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 53%.

The BAT light curve showed a complex structure with a duration of about ~30 sec.
T90 (15-350 keV) is 39.00 +- 7.28 sec (estimated error including systematics).

The time-averaged spectrum from -34.40 s to -20.56 s and -19.40s to 7.59 s is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.70 +- 0.22.  The fluence in the 15-150 keV band is 7.2 +- 1.1 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T+0.59 sec in the 15-150 keV band
is 1.3 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/BATbursts/1044678/bascript/top.html


GRB_name: GRB210425A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29899
SUBJECT: GRB 210425A: GECAM detection
DATE:    21/04/25 16:21:16 GMT
FROM:    QiBin Yi at IHEP, HXMT  <yiqb@ihep.ac.cn>

Q. B. Yi, S. L. Xiong, S. Xiao, C. Cai, Y. Zhao, J. C. Liu,
C. Y. Li, Y. Q. Zhang, W. C. Xue, C. Zheng, Z. W. Guo, X. Y. Zhao, Y. Huang,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, J. J. He,
B. Li, C. Li, J. H. Li, Q. X. Li, X. B. Li, X. Q. Li, Y. G. Li, X. H. Liang,
J. Y. Liao, J. C. Liu, X. J. Liu, Y. Q. Liu, F. J. Lu, Q. Luo, X. Ma,
G. Ou, W. X. Peng, R. Qiao, D. L. Shi, J. Y. Shi, L. M. Song,
X. Y. Song, G. X. Sun, X. L. Sun, Y. L. Tuo, C. W. Wang, J. Z. Wang,
P. Wang, X. Y. Wen, Y. B. Xu, Y. P. Xu, S. Yang, M. Yao,
B. X. Zhang, C. Y. Zhang, D. L. Zhang, Fan Zhang, Fei Zhang, H. M. Zhang,
K. Zhang, P. Zhang, S. N. Zhang, Z. Zhang, S. Y. Zhao,  S. J. Zheng,
X. Zhou (IHEP), report on behalf of GECAM team:

During the commissioning phase, GECAM-B triggered a short burst,
GRB 210425A, at 2021-04-25T07:07:04.200 UTC (denoted as T0).

GECAM alert data was promptly downlinked to the ground through the
short message service of BeiDou Navigation Satellite System (BDS).
The time latency of the first BeiDou message relative to the trigger time
is about 1 minute.

According to the BDS alert data, this burst mainly consists of 
a single pulse with a duration of about 0.5 s.  

An automatic in-flight localization was calculated using the light curves
and spectrum. Although the in-flight calibration of energy response and
localization has not been finalized yet, GECAM-B localized this burst to
the following position (J2000):
Ra: 67.5 deg Dec: -51.8 deg
Err: 2.7 deg (1-sigma, statistical only)
The current systematic error of location is estimated to be several degrees
which could be minimized by the ongoing calibration.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_lc_grd_all_combine_73033624.png

As the detailed science data are downloaded, all analyses would be improved.

Please note that all GECAM results here are preliminary. The final analysis
will be published in journal papers or GECAM online catalog.

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in
Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time),
which was funded by the Chinese Academy of Sciences (CAS).


GRB_name: GRB210420B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29901
SUBJECT: GRB 210420B: Assy optical observations
DATE:    21/04/25 22:56:09 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI), V. Kim (FAI, Pulkovo Observatory), M. Krugov (FAI), A. 
Pozanenko (IKI),  N. Pankov (HSE, IKI) report on behalf of GRB IKI FuN:

We observed the field of  GRB 210420B (Moss et al., GCN 29833; Lien et 
al., GCN 29854; Osborne et al. GCN 29876; Stamatikos et al., GCN29879) 
with AZT-20 telescope of Assy-Turgen observatory starting on 2021-04-23 
(UT) 18:39:00.

We marginally detect the optical afterglow  (Lipunov et al., GCN 29845; 
Oksanen et al., GCN 29846; Hu et al., GCN 29847; Tianrui Sun et al., GCN 
29848; Leonini et al., GCN 29851; de Ugarte Postigo et al., GCN 29852, 
29853; Watson et al., GCN 29858; Zheng et al., GCN 29861; Breeveld et 
al., GCN 29862; Stecklum et al., GCN 29863; Butler et al.,GCN 29864; 
Jelinek et al., GCN 29866; Watson, GCN 29867; Leonini et al., GCN 29872; 
Guelbenzu et al., GCN 29890; Pankov et al., GCN 29894; Ibrahimov et al., 
GCN 29895).

Preliminary photometry of the source (afterglow or afterglow + host 
galaxy)  is following

Date       UT start  t-T0       Exp.    Filter  OT    Err.  UL(3sigma)
                     (mid, days)  (s)

2021-04-23 18:39:00  2.98478    113*60  r'      23.2  0.3   23.3

The photometry is based on the nearby SDSS-DR12 stars
RA DEC r
16:56:42.09384 +42:38:35.9628 15.541
16:57:24.93456 +42:34:14.6388 16.642
16:56:58.03392 +42:33:40.5468 16.987


GRB_name: GRB210422B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29902
SUBJECT: GRB 210422B: Fermi GBM Final Localization
DATE:    21/04/26 15:06:47 GMT
FROM:    Boyan A. Hristov at UAH  <bah0046@uah.edu>

GRB 210422B: Fermi GBM Final Localization

The Fermi GBM Team reports the detection of a likely long GRB.

At 13:44:40.17 UT on 22 April 2021, the Fermi Gamma-Ray Burst Monitor
(GBM) triggered and located GRB 210422B (trigger 640791885 /
210422573).

This trigger coincides in time with INTEGRAL SPI-ACS trigger 9158.0
and CALET trigger 1303134201.

The on-ground calculated location, using the GBM trigger data, is
RA = 116.63, DEC = 24.71 (J2000 degrees, 7h 46m 31s, 24d 42' 36â€œ),
with a statistical uncertainty radius of 2.11 degrees.

The angle from the Fermi LAT boresight at the GBM trigger time is
62.00 degrees.

The GBM light curve consists of two peaks prominent in the range
10-300 keV.

A skymap can be found at:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210422573/quicklook/glg_skymap_all_bn210422573.png

HEALPix, including the estimated localization systematic:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210422573/quicklook/glg_healpix_all_bn210422573.fit

GBM light curve:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210422573/quicklook/glg_lc_medres34_bn210422573.gif


GRB_name: GRB210427A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29903
SUBJECT: GRB 210427A: Fermi GBM Final Real-time Localization
DATE:    21/04/27 05:07:38 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 04:57:12 UT on 27 Apr 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210427A (trigger 641192237.991858 / 210427206).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 177.3, Dec = -53.4 (J2000 degrees, equivalent to J2000 11h 49m, -53d 23'), with a statistical uncertainty of 1.1 degrees.

The angle from the Fermi LAT boresight is 146.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210427206/quicklook/glg_skymap_all_bn210427206.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210427206/quicklook/glg_healpix_all_bn210427206.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210427206/quicklook/glg_lc_medres34_bn210427206.gif


GRB_name: GRB210427A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29904
SUBJECT: Fermi GRB 210427A: Global MASTER-Net observations report 
DATE:    21/04/27 05:45:22 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-OAFA robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 210427A ( Fermi GBM team, GCN 29903) errorbox 83 sec after trigger time at 2021-04-27 04:58:36 UT, with upper limit up to  17.5 mag. The observations began at zenith distance = 41 deg. The sun  altitude  is -71.8 deg. 

The galactic latitude b =  8 deg., longitude l = 294 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1602343

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

      93 | 2021-04-27 04:58:36 |         MASTER-OAFA | (11h 30m 41.80s , -52d 41m 19.0s) |   C |    20 | 16.8 |        
     149 | 2021-04-27 04:59:26 |         MASTER-OAFA | (11h 35m 39.45s , -51d 53m 30.7s) |   C |    30 | 17.0 |        
     203 | 2021-04-27 05:00:15 |         MASTER-OAFA | (11h 35m 46.94s , -51d 53m 27.2s) |   C |    40 | 17.1 |        
     267 | 2021-04-27 05:01:15 |         MASTER-OAFA | (11h 35m 42.92s , -51d 51m 45.2s) |   C |    50 | 17.2 |        
     342 | 2021-04-27 05:02:25 |         MASTER-OAFA | (11h 35m 42.91s , -51d 53m 27.9s) |   C |    60 | 17.3 |        
     432 | 2021-04-27 05:03:45 |         MASTER-OAFA | (11h 35m 45.38s , -51d 51m 52.5s) |   C |    80 | 17.4 |        
     542 | 2021-04-27 05:05:24 |         MASTER-OAFA | (11h 35m 40.74s , -51d 52m 31.1s) |   C |   100 | 17.5 |        
     671 | 2021-04-27 05:07:24 |         MASTER-OAFA | (11h 47m 58.15s , -52d 31m 41.5s) |   C |   120 | 17.3 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210427A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29905
SUBJECT: GRB 210427A: BALROG localization (Fermi Trigger  / GRB 210427206)
DATE:    21/04/27 07:48:15 GMT
FROM:    Jochen Greiner at MPE,Garching  <jcg@mpe.mpg.de>

B. Biltzinger, F. Kunzweiler, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
 at 04:57:12 on 27 April 2021 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).

The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 172.6+/-2.5 deg
Decl.(2000.0) = -54.4+/-1.7 deg
We estimate an additional systematic error of 1 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210427206/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210427206/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210427206/json

                        


GRB_name: GRB210427A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29906
SUBJECT: GRB 210427A: GECAM detection
DATE:    21/04/27 10:03:19 GMT
FROM:    Shenglun Xie at IHEP  <xiesl@ihep.ac.cn>

S. L. Xie,Y. Huang, S. L. Xiong, S. Xiao, C. Cai, Y. Zhao, J. C. Liu,
C. Y. Li, Y. Q. Zhang, W. C. Xue, C. Zheng, Z. W. Guo, X. Y. Zhao,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, J. J. He,
B. Li, C. Li, J. H. Li, Q. X. Li, X. B. Li, X. Q. Li, Y. G. Li, X. H. Liang,
J. Y. Liao, J. C. Liu, X. J. Liu, Y. Q. Liu, F. J. Lu, Q. Luo, X. Ma,
G. Ou, W. X. Peng, R. Qiao, D. L. Shi, J. Y. Shi, L. M. Song,
X. Y. Song, G. X. Sun, X. L. Sun, Y. L. Tuo, C. W. Wang, J. Z. Wang,
P. Wang, X. Y. Wen, Y. B. Xu, Y. P. Xu, S. Yang, M. Yao, Q. B. Yi,
B. X. Zhang, C. Y. Zhang, D. L. Zhang, Fan Zhang, Fei Zhang, H. M. Zhang,
K. Zhang, P. Zhang, S. N. Zhang, Z. Zhang, S. Y. Zhao,  S. J. Zheng,
X. Zhou (IHEP), report on behalf of GECAM team:

During the commissioning phase, GECAM-B was triggered by a long GRB 210427A
at 2021-04-27T04:57:13.100 UTC (denoted as T0), 
which was also observed by Fermi/GBM (GCN #29903).

GECAM alert data was promptly downlinked to the ground through the
short message service of BeiDou Navigation Satellite System (BDS).
The time latency of the first BeiDou message relative to the trigger time
is about 1 minute.

According to the BDS alert data, this burst mainly consists of 
multiple pulses with a duration of about 20s.  

An automatic on-ground localization was calculated using the light curves
and spectrum. Although the in-flight calibration of energy response and
localization has not been finalized yet, GECAM-B localized this burst to
the following position (J2000):
ra: 175.26 deg
dec: -59.87 deg
err: 5.75 deg (statistical only)
The current systematic error of location is estimated to be several degrees
which could be minimized by the ongoing calibration.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_lc_grd_all_combine_73198633.png

As the detailed science data are downloaded, all analyses would be improved.

Please note that all GECAM results here are preliminary. The final analysis
will be published in journal papers or GECAM online catalog.

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in
Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time),
which was funded by the Chinese Academy of Sciences (CAS).


GRB_name: GRB210323B
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29908
SUBJECT: GRB 210323B: Swift-XRT observations
DATE:    21/04/27 17:32:50 GMT
FROM:    Aaron Tohuvavohu at U Toronto  <aaron.tohu@gmail.com>

M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), A. D'Ai
(INAF-IASFPA), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), D.N.
Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester),
A.P. Beardmore (U. Leicester) and P.A. Evans (U. Leicester) report on
behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Swift/BAT-GUANO-detected burst GRB 210323B (James DeLaunay et al. GCN
Circ. 29701), collecting 10.2 ks of Photon Counting (PC) mode data
between T0+100.8 ks and T0+1300 ks. 

One uncatalogued X-ray source has been detected consistent with being
within the Swift/BAT localization, it is below the RASS limit
and shows no definitive signs of fading. Therefore, at the present time
we cannot confirm this as the afterglow. Details of this source are
given below:

Source 1:
  RA (J2000):  259.6867  =  17:18:44.80
  Dec (J2000): +15.6339  =  +15:38:02.2
  Error: 4.6 arcsec (radius, 90% conf.)
  Count-rate: (1.18 [+0.71, -0.52])e-3 ct s^-1  
  Distance: 173 arcsec from Swift/BAT position.

Seven uncatalogued sources were also detected too far from the GRB
position to be likely afterglow candidates.

The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
https://www.swift.ac.uk/ToO_GRBs/00021426.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210424B
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29909
SUBJECT: IPN triangulation of GRB 210424B (short/hard)
DATE:    21/04/28 16:20:26 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

K. Hurley, on behalf of the IPN,

I. G. Mitrofanov, D. V. Golovin, A. S. Kozyrev, M. L. Litvak,
and A. B. Sanin, on behalf of the HEND-Odyssey GRB team,

D. Svinkin, S. Golenetskii, D. Frederiks, A. Ridnaia,
A. Lysenko, and T. Cline on behalf of the Konus-Wind team,

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,

and

W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:

The short-duration, very bright GRB 210424B
was detected by Konus-Wind, INTEGRAL (SPI-ACS), CALET (GBM),
and Mars-Odyssey (HEND) at about 28916 s UT (08:01:56).

We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   284.716 (18h 58m 52s) +16.172 (+16d 10' 20")
  Corners:
   284.892 (18h 59m 34s) +16.078 (+16d 04' 42")
   284.882 (18h 59m 32s) +16.153 (+16d 09' 09")
   284.540 (18h 58m 10s) +16.265 (+16d 15' 55")
   284.550 (18h 58m 12s) +16.191 (+16d 11' 28")
  ---------------------------------------------
The error box area is 84 sq. arcmin, and its maximum
dimension is 23 arcmin (the minimum one is 4 arcmin).
The Sun distance was 102 deg.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB210424_T28916/IPN

The time history and spectrum will be given in forthcoming
GCN Circulars.


GRB_name: GRB210424B
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29911
SUBJECT: Konus-Wind detection of GRB 210424B
DATE:    21/04/29 12:54:06 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

D. Svinkin, S. Golenetskii, D. Frederiks, M. Ulanov,
A. Tsvetkova, A. Lysenko, A. Ridnaia, and T. Cline
on behalf of the Konus-Wind team, report:

The short-duration, very bright GRB 210424B
(IPN triangulation: Hurley et al., GCN Circ. 29909)
triggered Konus-Wind at T0=28916.081 s UT (08:01:56.081).

The burst light curve shows a multi-peaked structure
which starts at ~T0-0.1 s and has a total duration of ~1.6 s.
The emission is seen up to ~10 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210424_T28916/

As observed by Konus-Wind, the burst
had a fluence of 8.91(-0.83,+0.93)x10^-6 erg/cm2,
and a 16-ms peak flux, measured from T0+0.800 s,
of 3.13(-0.52,+0.54)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+1.024 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.39(-0.17,+0.20),
the high energy photon index beta = -2.76(-0.45,+0.25),
the peak energy Ep = 198(-21,+23) keV
(chi2 = 62/55 dof).

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.


GRB_name: GRB210413B
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29912
SUBJECT: GRB 210413B: Swift/UVOT Observations
DATE:    21/04/30 00:54:43 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M. H. Siegel (PSU) and A. Tohuvavohu (U Toronto) report on behalf of the Swift/UVOT team:

Swift/UVOT performed follow-up observations of the Swift/BAT-detected burst GRB 210413B
(Tohuvavohu et al., GCN Circ. 29819) 185 ks after the BAT trigger. We detect a faint source
close to the XRT source reported by Kennea et al. (GCN Circ. 29827).

The preliminary UVOT position is:
   RA  (J2000) =  12:10:07.75 = 182.53230 (deg.)
   Dec (J2000) = +56:02:58.9  = 56.04970 (deg.)
with an estimated uncertainty of 0.4 arc sec. (radius, 90% confidence).

The preliminary detection using the UVOT photometric system (Breeveld et al. 2011, AIP Conf.
Proc. 1358, 373) is wh=19.68+-0.03 mag (Vega) or wh=20.48+-0.03 mag (AB).

We note, however, that the DECaLs survey shows faint source at this position at a g magnitude
of 21.09 mag  (AB).  It is thus not clear if this detection represents a brightening of that source,
which could indicate a host galaxy.


GRB_name: GRB210424B
Detection_method: CALET
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29913
SUBJECT: GRB 210424B: CALET Gamma-Ray Burst Monitor detection
DATE:    21/04/30 12:32:09 GMT
FROM:    Valentin Pal'shin at AGU  <val@phys.aoyama.ac.jp>

A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (AGU),
Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN),
Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U),
Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC),
M. L. Cherry (LSU), S. Ricciarini (U of Florence),
P. S. Marrocchesi (U of Siena),
and the CALET collaboration:

The short GRB 210424B (IPN triangulation: Hurley, GCN Circ. 29909;
Konus-Wind detection: Svinkin et al., GCN Circ. 29911) triggered the CALET
Gamma-ray Burst Monitor (CGBM) at 08:01:55.115 UTC on 24 April 2021
(http://cgbm.calet.jp/cgbm_trigger/flight/1303286436/). The burst signal
was seen mainly by the SGM detector.
The burst light curve shows a multi-peaked structure which starts
at T+0.40 sec, peaks at 1.28 sec and ends at T+1.42 sec.
The T90 and T50 durations measured by the SGM data are 1.04 +- 0.16 sec
and 0.56 +- 0.15 sec (40-1000 keV), respectively.

The ground processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1303286436/

The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at the Waseda University.


GRB_name: GRB210430A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29914
SUBJECT: GRB 210430A: Swift detection of a burst
DATE:    21/04/30 13:19:58 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

B. Sbarufatti (PSU), A. Y. Lien (GSFC/UMBC) and
A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 10:42:10 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210430A (trigger= 1046014).  Swift did not slew immediately
due to an observing constraint. 
The BAT on-board calculated location is 
RA, Dec 57.178, +45.074 which is 
   RA(J2000) = 03h 48m 43s
   Dec(J2000) = +45d 03' 31"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  With the currently available data from
~T-50 s to ~T+30 s, the BAT light curve showed a single-peaked
structure with a duration of about 10 sec.  The peak count rate
was ~500 counts/sec (15-350 keV), at ~2 sec after the trigger. 

The BAT position is sun-constrained for Swift until July 8 2021,
there will be no XRT or UVOT followup before this time. 

Burst Advocate for this burst is B. Sbarufatti (bxs60 AT psu.edu). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB210430B
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29916
SUBJECT: GRB 210430B: Fermi GBM Final Real-time Localization
DATE:    21/04/30 21:52:37 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 21:42:17 UT on 30 Apr 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210430B (trigger 641511742.665196 / 210430904).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 348.2, Dec = 8.3 (J2000 degrees, equivalent to J2000 23h 12m, 8d 18'), with a statistical uncertainty of 6.5 degrees.

The angle from the Fermi LAT boresight is 76.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210430904/quicklook/glg_skymap_all_bn210430904.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210430904/quicklook/glg_healpix_all_bn210430904.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210430904/quicklook/glg_lc_medres34_bn210430904.gif


GRB_name: GRB210430B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29917
SUBJECT: Fermi GRB 210430B: Global MASTER-Net observations report 
DATE:    21/04/30 23:45:14 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-Kislovodsk robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 210430B ( Fermi GBM team, GCN 29916) errorbox  6673 sec after notice time and 6710 sec after trigger time at 2021-04-30 23:34:08 UT, with upper limit up to  17.1 mag. The observations began at zenith distance = 79 deg. The sun  altitude  is -23.0 deg. 

The galactic latitude b = -47 deg., longitude l = 86 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1604728

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

    6741 | 2021-04-30 23:34:08 |   MASTER-Kislovodsk | (22h 47m 52.89s , +14d 03m 13.2s) |   C |    60 | 16.9 |        
    6741 | 2021-04-30 23:34:08 |   MASTER-Kislovodsk | (22h 51m 45.19s , +13d 39m 00.0s) |   C |    60 | 17.1 |        
    6901 | 2021-04-30 23:36:49 |   MASTER-Kislovodsk | (22h 43m 52.25s , +10d 04m 18.5s) |   C |    60 | 16.9 |        
    6901 | 2021-04-30 23:36:49 |   MASTER-Kislovodsk | (22h 47m 40.74s , +09d 40m 01.6s) |   C |    60 | 16.9 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210430A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29918
SUBJECT: GRB 210430A: Swift-BAT refined analysis
DATE:    21/05/01 00:02:11 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

H. A. Krimm (NSF), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), S. Laha (GSFC/UMBC),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
B. Sbarufatti (PSU), M. Stamatikos (OSU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-240 to T+962 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 210430A (trigger #1046014)
(Sbarufatti et al., GCN Circ. 29914).  The BAT ground-calculated
position is RA, Dec = 57.185, 45.080 deg which is
   RA(J2000)  =  03h 48m 44.3s
   Dec(J2000) = +45d 04' 46.9"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 25%.

The mask-weighted light curve shows a single-peaked structure
that starts at ~T-3 s, peaks at ~T+2 s, and ends at ~T+15 s.
T90 (15-350 keV) is 11.53 +- 2.83 sec (estimated error including
systematics).

The time-averaged spectrum from T-2.72 to T+14.60 sec is best fit
by a simple power-law model.  The power law index of the time-averaged
spectrum is 2.15 +- 0.21.  The fluence in the 15-150 keV band is
9.9 +- 1.3 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from
T+1.14 sec in the 15-150 keV band is 1.9 +- 0.4 ph/cm2/sec.  All the
quoted errors are at the 90% confidence level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1046014/BA/


GRB_name: GRB210501A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29919
SUBJECT: GRB 210501A: Fermi GBM Final Real-time Localization
DATE:    21/05/01 05:05:20 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 04:55:00 UT on 1 May 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210501A (trigger 641537705.291634 / 210501205).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 357.8, Dec = -71.3 (J2000 degrees, equivalent to J2000 23h 51m, -71d 17'), with a statistical uncertainty of 11.7 degrees.

The angle from the Fermi LAT boresight is 49.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210501205/quicklook/glg_skymap_all_bn210501205.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210501205/quicklook/glg_healpix_all_bn210501205.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210501205/quicklook/glg_lc_medres34_bn210501205.gif


GRB_name: GRB210424B
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29920
SUBJECT: GRB 210424B: MITSuME Akeno optical upper limits
DATE:    21/05/01 12:26:07 GMT
FROM:    Katsuhiro L. Murata at Nagoya U  <murata@u.phys.nagoya-u.ac.jp>

R. Hosokawa, Y. Imai, K. L. Murata, M. Niwano, N. Ito, H. Takamatsu, S.
Sato, M. Takaku, R. Noto, R. Yamaguchi, Y. Yatsu, and N. Kawai (TokyoTech)
report on behalf of the MITSuME collaboration:

We observed the field of GRB 210424B (IPN triangulation: Hurley et al. GCN
Circular #29909, Konus-Wind detection: Svinkin et al. GCN Circular #29911,
CALET Gamma-Ray Burst Monitor detection: Yoshida et al. GCN Circular
#29913) with the optical three color (g', Rc, and Ic) CCD cameras attached
to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan. The
observation with a series of 60 sec exposures started at 2021-04-29
16:49:39 UT (5.35 days after the triggers). We stacked the images with good
conditions. We did not detect any uncatalogued sources within the IPN
triangulation error box (Hurley et al. GCN Circular #29909) in all three
bands. We obtained the 5-sigma limits of the stacked images as follows.

T0+[day] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
5.35 2021-04-29 17:05 1020 g'>18.5, Rc>18.4, Ic>17.8
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used the PS1 catalog for flux calibration. The magnitudes are expressed
in the AB system. The images were processed in real-time through the
MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1,
Pages 4-24; https://github.com/MNiwano/Eclaire).


GRB_name: GRB210430A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29921
SUBJECT: GRB 210430A: BOOTES-1 optical limit
DATE:    21/05/01 18:10:01 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

T.-R Sun, Y.-D. Hu, E. Fernandez-Garcia, A. J. Castro-Tirado, M.D. Caballero-Garcia, M. A. Castro Tirado, F. Rendon (IAA-CSIC), C. Perez del Pulgar, A. Castellon and A. J. Reina (Univ. de Malaga)  on behalf of a larger collaboration, report:

Following the detection of GRB 210430A by Swift (Moss et al. GCNC 29918), we triggered the 0.3m BOOTES-1B robotic telescope at the BOOTES-1 astronomical station at ESAt/INTA-CEDEA in Mazagn (Huelva, Spain), gathering images starting on Apr 30, 20:30 UT, about 9.8 hours after the onset of the GRB. After co-adding the corresponding images, nothing is found within the GRB 210430A error box down to 18.4 limiting magnitude, after calibrating the image with G mag in the GAIA DR2 catalogue.

We thank the staff at INTA-CEDEA for their excellent support.


GRB_name: GRB210501A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29923
SUBJECT: Fermi GRB 210501A: Global MASTER-Net observations report 
DATE:    21/05/02 06:30:15 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-OAFA robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 210501A ( Fermi GBM team, GCN 29919) errorbox  228 sec after notice time and 264 sec after trigger time at 2021-05-01 04:59:25 UT, with upper limit up to  17.6 mag. The observations began at zenith distance = 78 deg. The sun  altitude  is -72.9 deg. 

The galactic latitude b = -45 deg., longitude l = 310 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1604874

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

     295 | 2021-05-01 04:59:25 |         MASTER-OAFA | (02h 07m 36.48s , -70d 48m 13.7s) |   C |    60 | 17.0 |        
     565 | 2021-05-01 05:03:55 |         MASTER-OAFA | (01h 20m 33.72s , -69d 28m 12.6s) |   C |    60 | 17.0 |        
    1145 | 2021-05-01 05:13:35 |         MASTER-OAFA | (02h 31m 07.34s , -69d 27m 27.5s) |   C |    60 | 17.0 |        
    1648 | 2021-05-01 05:21:58 |         MASTER-OAFA | (01h 44m 04.29s , -69d 26m 51.4s) |   C |    60 | 17.1 |        
    2400 | 2021-05-01 05:34:30 |         MASTER-OAFA | (02h 07m 33.64s , -69d 27m 38.6s) |   C |    60 | 17.1 |        
    2493 | 2021-05-01 05:36:03 |         MASTER-OAFA | (01h 20m 32.46s , -70d 47m 32.9s) |   C |    60 | 16.9 |        
    2586 | 2021-05-01 05:37:36 |         MASTER-OAFA | (02h 31m 09.78s , -69d 27m 57.4s) |   C |    60 | 17.0 |        
    2678 | 2021-05-01 05:39:08 |         MASTER-OAFA | (01h 44m 01.98s , -70d 49m 17.2s) |   C |    60 | 17.0 |        
    2778 | 2021-05-01 05:40:48 |         MASTER-OAFA | (23h 46m 30.62s , -69d 25m 42.7s) |   C |    60 | 17.4 |        
    2872 | 2021-05-01 05:42:22 |         MASTER-OAFA | (00h 10m 04.24s , -70d 49m 09.5s) |   C |    60 | 17.3 |        
    2971 | 2021-05-01 05:44:00 |         MASTER-OAFA | (23h 09m 41.67s , -69d 25m 57.8s) |   C |    60 | 17.5 |        
    3063 | 2021-05-01 05:45:33 |         MASTER-OAFA | (23h 33m 17.56s , -70d 47m 21.1s) |   C |    60 | 17.4 |        
    3158 | 2021-05-01 05:47:07 |         MASTER-OAFA | (23h 47m 27.26s , -67d 27m 20.7s) |   C |    60 | 17.2 |        
    3251 | 2021-05-01 05:48:41 |         MASTER-OAFA | (00h 09m 07.69s , -68d 48m 53.1s) |   C |    60 | 17.4 |        
    3343 | 2021-05-01 05:50:13 |         MASTER-OAFA | (02h 07m 35.83s , -69d 26m 47.5s) |   C |    60 | 17.0 |        
    3435 | 2021-05-01 05:51:45 |         MASTER-OAFA | (01h 20m 35.02s , -70d 49m 00.1s) |   C |    60 | 16.9 |        
    3529 | 2021-05-01 05:53:19 |         MASTER-OAFA | (02h 31m 08.62s , -69d 26m 55.7s) |   C |    60 | 17.0 |        
    3622 | 2021-05-01 05:54:52 |         MASTER-OAFA | (01h 44m 00.88s , -70d 48m 08.5s) |   C |    60 | 17.1 |        
    3720 | 2021-05-01 05:56:30 |         MASTER-OAFA | (23h 46m 28.19s , -69d 25m 20.9s) |   C |    60 | 17.4 |        
    3818 | 2021-05-01 05:58:08 |         MASTER-OAFA | (00h 10m 08.31s , -70d 48m 28.1s) |   C |    60 | 17.3 |        
    3915 | 2021-05-01 05:59:45 |         MASTER-OAFA | (23h 09m 42.87s , -69d 26m 45.9s) |   C |    60 | 17.5 |        
    4013 | 2021-05-01 06:01:23 |         MASTER-OAFA | (23h 33m 24.37s , -70d 48m 56.7s) |   C |    60 | 17.5 |        
    4105 | 2021-05-01 06:02:55 |         MASTER-OAFA | (23h 47m 31.12s , -67d 25m 07.6s) |   C |    60 | 17.3 |        
    4197 | 2021-05-01 06:04:27 |         MASTER-OAFA | (23h 17m 01.62s , -68d 46m 58.7s) |   C |    60 | 17.4 |        
    4290 | 2021-05-01 06:06:00 |         MASTER-OAFA | (00h 08m 55.57s , -67d 26m 17.9s) |   C |    60 | 17.2 |        
    4381 | 2021-05-01 06:07:31 |         MASTER-OAFA | (23h 38m 23.54s , -68d 47m 05.6s) |   C |    60 | 17.4 |        
    4473 | 2021-05-01 06:09:03 |         MASTER-OAFA | (00h 33m 30.02s , -69d 27m 42.9s) |   C |    60 | 17.1 |        
    4566 | 2021-05-01 06:10:36 |         MASTER-OAFA | (00h 57m 10.03s , -70d 49m 04.5s) |   C |    60 | 16.9 |        
    4662 | 2021-05-01 06:12:12 |         MASTER-OAFA | (23h 48m 21.23s , -65d 26m 23.6s) |   C |    60 | 17.1 |        
    4757 | 2021-05-01 06:13:47 |         MASTER-OAFA | (23h 46m 38.74s , -70d 47m 26.9s) |   C |    60 | 17.4 |        
    4850 | 2021-05-01 06:15:20 |         MASTER-OAFA | (00h 08m 02.84s , -65d 25m 57.1s) |   C |    60 | 17.0 |        
    4941 | 2021-05-01 06:16:51 |         MASTER-OAFA | (00h 10m 02.89s , -70d 47m 20.9s) |   C |    60 | 17.2 |        
    5021 | 2021-05-01 06:18:11 |         MASTER-OAFA | (23h 09m 56.11s , -70d 47m 59.1s) |   C |    60 | 17.6 |        
    5117 | 2021-05-01 06:19:47 |         MASTER-OAFA | (23h 33m 13.17s , -69d 26m 54.7s) |   C |    60 | 17.4 |        
    5214 | 2021-05-01 06:21:24 |         MASTER-OAFA | (23h 47m 42.99s , -68d 49m 04.5s) |   C |    60 | 17.4 |        
    5294 | 2021-05-01 06:22:44 |         MASTER-OAFA | (23h 17m 01.88s , -68d 46m 57.3s) |   C |    60 | 17.6 |        
    5387 | 2021-05-01 06:24:17 |         MASTER-OAFA | (00h 08m 58.20s , -67d 26m 43.3s) |   C |    60 | 17.2 |        
    5479 | 2021-05-01 06:25:49 |         MASTER-OAFA | (23h 38m 31.51s , -68d 47m 11.1s) |   C |    60 | 17.5 |        
    5573 | 2021-05-01 06:27:22 |         MASTER-OAFA | (00h 33m 29.31s , -69d 26m 27.8s) |   C |    60 | 17.1 |        
    5669 | 2021-05-01 06:28:59 |         MASTER-OAFA | (00h 57m 05.51s , -70d 47m 16.2s) |   C |    60 | 17.0 |        
    5768 | 2021-05-01 06:30:37 |         MASTER-OAFA | (23h 48m 24.04s , -65d 25m 36.7s) |   C |    60 | 17.1 |        
    5863 | 2021-05-01 06:32:13 |         MASTER-OAFA | (00h 08m 13.75s , -66d 49m 02.5s) |   C |    60 | 17.0 |        
    5943 | 2021-05-01 06:33:32 |         MASTER-OAFA | (23h 24m 35.96s , -66d 47m 10.7s) |   C |    60 | 17.2 |        
    6037 | 2021-05-01 06:35:07 |         MASTER-OAFA | (23h 44m 09.84s , -65d 26m 26.8s) |   C |    60 | 16.8 |        
    6139 | 2021-05-01 06:36:48 |         MASTER-OAFA | (00h 30m 32.58s , -68d 48m 04.5s) |   C |    60 | 17.0 |        
    6238 | 2021-05-01 06:38:28 |         MASTER-OAFA | (00h 51m 49.61s , -67d 25m 11.8s) |   C |    60 | 16.8 |        
    6333 | 2021-05-01 06:40:02 |         MASTER-OAFA | (23h 17m 03.78s , -68d 47m 53.6s) |   C |    60 | 17.4 |        
    6412 | 2021-05-01 06:41:22 |         MASTER-OAFA | (23h 38m 26.04s , -68d 48m 57.7s) |   C |    60 | 17.3 |        
    6505 | 2021-05-01 06:42:55 |         MASTER-OAFA | (00h 33m 36.39s , -69d 26m 59.9s) |   C |    60 | 17.1 |        
    6599 | 2021-05-01 06:44:29 |         MASTER-OAFA | (00h 57m 09.37s , -70d 47m 31.9s) |   C |    60 | 16.8 |        
    6694 | 2021-05-01 06:46:04 |         MASTER-OAFA | (23h 48m 22.25s , -65d 26m 11.0s) |   C |    60 | 17.2 |        
    6787 | 2021-05-01 06:47:37 |         MASTER-OAFA | (00h 08m 21.53s , -66d 47m 18.1s) |   C |    60 | 17.2 |        
    7076 | 2021-05-01 06:52:26 |         MASTER-OAFA | (23h 24m 33.58s , -66d 46m 57.4s) |   C |    60 | 17.1 |        
    7156 | 2021-05-01 06:53:46 |         MASTER-OAFA | (23h 44m 26.02s , -66d 47m 59.0s) |   C |    60 | 17.2 |        
    7250 | 2021-05-01 06:55:19 |         MASTER-OAFA | (00h 30m 21.95s , -67d 26m 53.6s) |   C |    60 | 17.1 |        
    7348 | 2021-05-01 06:56:58 |         MASTER-OAFA | (00h 52m 06.45s , -68d 48m 44.6s) |   C |    60 | 17.3 |        
    7643 | 2021-05-01 07:01:52 |         MASTER-OAFA | (22h 23m 01.92s , -70d 46m 43.1s) |   C |    60 | 17.4 |        
    7723 | 2021-05-01 07:03:12 |         MASTER-OAFA | (22h 34m 09.11s , -68d 46m 35.9s) |   C |    60 | 17.5 |        
    7802 | 2021-05-01 07:04:32 |         MASTER-OAFA | (22h 46m 32.23s , -70d 47m 41.2s) |   C |    60 | 17.4 |        
    7882 | 2021-05-01 07:05:52 |         MASTER-OAFA | (22h 55m 34.77s , -68d 48m 44.8s) |   C |    60 | 17.4 |        
    7962 | 2021-05-01 07:07:12 |         MASTER-OAFA | (00h 28m 06.05s , -66d 47m 03.9s) |   C |    60 | 17.0 |        
    8055 | 2021-05-01 07:08:44 |         MASTER-OAFA | (00h 47m 35.81s , -65d 26m 25.9s) |   C |    60 | 16.4 |        
    8144 | 2021-05-01 07:10:14 |         MASTER-OAFA | (23h 24m 39.19s , -66d 47m 13.0s) |   C |    60 | 17.0 |        
    8223 | 2021-05-01 07:11:33 |         MASTER-OAFA | (23h 44m 19.70s , -66d 47m 55.7s) |   C |    60 | 16.7 |        
    8320 | 2021-05-01 07:13:10 |         MASTER-OAFA | (00h 30m 23.37s , -67d 24m 41.3s) |   C |    60 | 16.4 |        
    8426 | 2021-05-01 07:14:56 |         MASTER-OAFA | (00h 52m 07.62s , -68d 47m 55.0s) |   C |    60 | 16.2 |        
    8708 | 2021-05-01 07:19:38 |         MASTER-OAFA | (22h 23m 01.53s , -70d 48m 14.5s) |   C |    60 | 16.8 |        
    8788 | 2021-05-01 07:20:57 |         MASTER-OAFA | (22h 34m 11.55s , -68d 46m 38.2s) |   C |    60 | 16.7 |        
    8867 | 2021-05-01 07:22:17 |         MASTER-OAFA | (22h 46m 29.64s , -70d 48m 35.8s) |   C |    60 | 16.7 |        
    8947 | 2021-05-01 07:23:37 |         MASTER-OAFA | (22h 55m 42.17s , -68d 46m 51.8s) |   C |    60 | 16.7 |        
    9041 | 2021-05-01 07:25:10 |         MASTER-OAFA | (00h 27m 48.94s , -65d 25m 25.3s) |   C |    60 | 16.4 |        
    9135 | 2021-05-01 07:26:44 |         MASTER-OAFA | (00h 47m 47.76s , -66d 46m 47.3s) |   C |    60 | 16.3 |        
    9214 | 2021-05-01 07:28:04 |         MASTER-OAFA | (22h 45m 05.75s , -66d 48m 43.3s) |   C |    60 | 16.5 |        
    9294 | 2021-05-01 07:29:23 |         MASTER-OAFA | (23h 04m 57.08s , -66d 48m 20.5s) |   C |    60 | 16.4 |        
    9375 | 2021-05-01 07:30:45 |         MASTER-OAFA | (23h 32m 41.39s , -64d 48m 47.7s) |   C |    60 | 16.4 |        
    9455 | 2021-05-01 07:32:05 |         MASTER-OAFA | (23h 51m 04.23s , -64d 47m 13.9s) |   C |    60 | 16.4 |        
    9534 | 2021-05-01 07:33:24 |         MASTER-OAFA | (23h 49m 15.55s , -64d 46m 53.7s) |   C |    60 | 16.5 |        
    9616 | 2021-05-01 07:34:45 |         MASTER-OAFA | (00h 07m 41.78s , -64d 47m 51.7s) |   C |    60 | 16.3 |        
    9707 | 2021-05-01 07:36:17 |         MASTER-OAFA | (22h 22m 38.76s , -69d 25m 47.4s) |   C |    60 | 16.3 |        
    9787 | 2021-05-01 07:37:37 |         MASTER-OAFA | (22h 34m 00.48s , -67d 25m 23.5s) |   C |    60 | 16.2 |        
    9880 | 2021-05-01 07:39:10 |         MASTER-OAFA | (22h 46m 31.09s , -70d 47m 08.9s) |   C |    60 | 16.4 |        
    9962 | 2021-05-01 07:40:31 |         MASTER-OAFA | (22h 55m 40.42s , -68d 48m 16.1s) |   C |    60 | 16.6 |        
   10041 | 2021-05-01 07:41:51 |         MASTER-OAFA | (00h 28m 11.16s , -66d 47m 07.7s) |   C |    60 | 16.5 |        
   10137 | 2021-05-01 07:43:27 |         MASTER-OAFA | (00h 47m 34.46s , -65d 25m 17.9s) |   C |    60 | 16.1 |        
   10227 | 2021-05-01 07:44:57 |         MASTER-OAFA | (22h 45m 04.53s , -66d 46m 40.8s) |   C |    60 | 16.4 |        
   10307 | 2021-05-01 07:46:17 |         MASTER-OAFA | (23h 04m 55.39s , -66d 47m 49.5s) |   C |    60 | 16.3 |        
   10387 | 2021-05-01 07:47:36 |         MASTER-OAFA | (23h 32m 37.41s , -64d 48m 56.2s) |   C |    60 | 15.8 |        
   10466 | 2021-05-01 07:48:56 |         MASTER-OAFA | (23h 51m 04.38s , -64d 48m 48.5s) |   C |    60 | 16.2 |        
   10546 | 2021-05-01 07:50:16 |         MASTER-OAFA | (23h 49m 18.27s , -64d 47m 10.8s) |   C |    60 | 16.3 |        
   10626 | 2021-05-01 07:51:36 |         MASTER-OAFA | (00h 07m 37.88s , -64d 48m 45.2s) |   C |    60 | 16.1 |        
   10706 | 2021-05-01 07:52:56 |         MASTER-OAFA | (22h 55m 59.90s , -64d 47m 50.0s) |   C |    60 | 16.2 |        
   10785 | 2021-05-01 07:54:15 |         MASTER-OAFA | (23h 14m 18.65s , -64d 46m 54.4s) |   C |    60 | 16.3 |        
   10865 | 2021-05-01 07:55:35 |         MASTER-OAFA | (00h 25m 53.49s , -64d 48m 50.4s) |   C |    60 | 16.3 |        
   10945 | 2021-05-01 07:56:55 |         MASTER-OAFA | (00h 44m 19.79s , -64d 48m 27.8s) |   C |    60 | 16.1 |        
   11039 | 2021-05-01 07:58:29 |         MASTER-OAFA | (01h 13m 20.83s , -67d 26m 10.9s) |   C |    60 | 15.9 |        
   11137 | 2021-05-01 08:00:07 |         MASTER-OAFA | (01h 35m 04.78s , -68d 46m 49.0s) |   C |    60 | 15.6 |        
   11233 | 2021-05-01 08:01:43 |         MASTER-OAFA | (22h 44m 52.48s , -65d 24m 48.1s) |   C |    60 | 16.4 |        
   11344 | 2021-05-01 08:03:33 |         MASTER-OAFA | (01h 07m 26.42s , -65d 25m 02.0s) |   C |    60 | 15.5 |        
   11434 | 2021-05-01 08:05:04 |         MASTER-OAFA | (23h 04m 50.06s , -66d 48m 50.5s) |   C |    60 | 15.8 |        
   11514 | 2021-05-01 08:06:24 |         MASTER-OAFA | (23h 32m 44.01s , -64d 48m 41.4s) |   C |    60 | 15.7 |        
   11600 | 2021-05-01 08:07:49 |         MASTER-OAFA | (01h 27m 22.11s , -66d 46m 49.6s) |   C |    60 | 16.3 |        
   11679 | 2021-05-01 08:09:09 |         MASTER-OAFA | (23h 51m 02.30s , -64d 48m 44.7s) |   C |    60 | 16.3 |        
   11759 | 2021-05-01 08:10:29 |         MASTER-OAFA | (23h 41m 13.62s , -62d 47m 59.4s) |   C |    60 | 16.2 |        
   11839 | 2021-05-01 08:11:49 |         MASTER-OAFA | (23h 49m 17.96s , -64d 46m 58.1s) |   C |    60 | 16.3 |        
   11919 | 2021-05-01 08:13:09 |         MASTER-OAFA | (00h 07m 42.47s , -64d 47m 54.2s) |   C |    60 | 16.2 |        
   12007 | 2021-05-01 08:14:36 |         MASTER-OAFA | (22h 56m 02.63s , -64d 48m 50.7s) |   C |    60 | 16.4 |        
   12086 | 2021-05-01 08:15:56 |         MASTER-OAFA | (23h 14m 27.54s , -64d 48m 54.3s) |   C |    60 | 16.1 |        
   12474 | 2021-05-01 08:22:23 |         MASTER-OAFA | (23h 58m 19.91s , -62d 46m 54.8s) |   C |    60 | 16.1 |        
   12553 | 2021-05-01 08:23:43 |         MASTER-OAFA | (00h 26m 01.66s , -64d 47m 47.9s) |   C |    60 | 16.0 |        
   12633 | 2021-05-01 08:25:03 |         MASTER-OAFA | (00h 44m 14.59s , -64d 48m 39.9s) |   C |    60 | 16.0 |        
   12714 | 2021-05-01 08:26:24 |         MASTER-OAFA | (01h 13m 39.42s , -68d 47m 57.5s) |   C |    60 | 16.0 |        
   12808 | 2021-05-01 08:27:57 |         MASTER-OAFA | (01h 34m 48.70s , -67d 24m 23.6s) |   C |    60 | 15.7 |        
   12901 | 2021-05-01 08:29:30 |         MASTER-OAFA | (01h 07m 37.15s , -66d 48m 07.1s) |   C |    60 | 16.1 |        
   12981 | 2021-05-01 08:30:50 |         MASTER-OAFA | (01h 27m 25.75s , -66d 46m 24.1s) |   C |    60 | 15.8 |        
   13396 | 2021-05-01 08:37:46 |         MASTER-OAFA | (23h 41m 12.93s , -62d 47m 07.8s) |   C |    60 | 16.1 |        
   13884 | 2021-05-01 08:45:54 |         MASTER-OAFA | (22h 56m 06.36s , -64d 48m 31.6s) |   C |    60 | 16.5 |        
   14213 | 2021-05-01 08:51:23 |         MASTER-OAFA | (23h 58m 19.17s , -62d 47m 03.8s) |   C |    60 | 16.4 |        
   14299 | 2021-05-01 08:52:49 |         MASTER-OAFA | (00h 26m 00.39s , -64d 47m 58.0s) |   C |    60 | 16.3 |        
   14378 | 2021-05-01 08:54:08 |         MASTER-OAFA | (00h 44m 15.83s , -64d 48m 48.8s) |   C |    60 | 16.2 |        
   17290 | 2021-05-01 09:42:39 |         MASTER-OAFA | (01h 13m 45.77s , -68d 47m 24.7s) |   C |    60 | 15.0 |        
   17369 | 2021-05-01 09:43:59 |         MASTER-OAFA | (01h 35m 05.22s , -68d 48m 11.1s) |   C |    60 | 15.0 |        
   17449 | 2021-05-01 09:45:19 |         MASTER-OAFA | (01h 07m 46.00s , -66d 48m 11.8s) |   C |    60 | 15.1 |        
   17529 | 2021-05-01 09:46:39 |         MASTER-OAFA | (01h 27m 27.20s , -66d 46m 22.8s) |   C |    60 | 14.9 |        
   17613 | 2021-05-01 09:48:03 |         MASTER-OAFA | (23h 41m 19.26s , -62d 49m 03.3s) |   C |    60 | 15.8 |        
   17693 | 2021-05-01 09:49:23 |         MASTER-OAFA | (23h 58m 28.33s , -62d 47m 18.2s) |   C |    60 | 15.8 |        
   17773 | 2021-05-01 09:50:43 |         MASTER-OAFA | (23h 49m 54.20s , -62d 47m 17.6s) |   C |    60 | 15.7 |        
   17853 | 2021-05-01 09:52:02 |         MASTER-OAFA | (00h 07m 07.33s , -62d 48m 14.1s) |   C |    60 | 15.4 |        
   17933 | 2021-05-01 09:53:22 |         MASTER-OAFA | (23h 07m 09.86s , -62d 48m 52.9s) |   C |    60 | 15.7 |        
   18012 | 2021-05-01 09:54:42 |         MASTER-OAFA | (23h 24m 13.09s , -62d 47m 45.0s) |   C |    60 | 15.2 |        
   18092 | 2021-05-01 09:56:02 |         MASTER-OAFA | (21h 51m 21.97s , -68d 47m 07.9s) |   C |    60 | 15.7 |        
   18171 | 2021-05-01 09:57:21 |         MASTER-OAFA | (22h 12m 41.92s , -68d 48m 07.2s) |   C |    60 | 15.7 |        
   18251 | 2021-05-01 09:58:41 |         MASTER-OAFA | (22h 05m 43.96s , -66d 48m 04.8s) |   C |    60 | 15.6 |        
   18331 | 2021-05-01 10:00:01 |         MASTER-OAFA | (22h 25m 22.77s , -66d 49m 14.3s) |   C |    60 | 15.6 |        
   18414 | 2021-05-01 10:01:24 |         MASTER-OAFA | (21h 36m 02.99s , -70d 46m 26.5s) |   C |    60 | 15.5 |        
   18494 | 2021-05-01 10:02:43 |         MASTER-OAFA | (00h 24m 11.39s , -62d 47m 19.1s) |   C |    60 | 15.0 |        
   18573 | 2021-05-01 10:04:03 |         MASTER-OAFA | (21h 59m 30.54s , -70d 47m 16.7s) |   C |    60 | 15.0 |        
   18653 | 2021-05-01 10:05:23 |         MASTER-OAFA | (00h 41m 12.08s , -62d 47m 01.7s) |   C |    60 | 14.3 |        
   18733 | 2021-05-01 10:06:42 |         MASTER-OAFA | (23h 49m 59.91s , -62d 48m 22.1s) |   C |    60 | 14.7 |        
   18812 | 2021-05-01 10:08:02 |         MASTER-OAFA | (00h 07m 00.73s , -62d 49m 17.1s) |   C |    60 | 14.5 |        
   18892 | 2021-05-01 10:09:22 |         MASTER-OAFA | (23h 07m 09.13s , -62d 48m 58.2s) |   C |    60 | 14.7 |        
   18972 | 2021-05-01 10:10:42 |         MASTER-OAFA | (23h 24m 12.78s , -62d 47m 43.8s) |   C |    60 | 14.7 |        
   19053 | 2021-05-01 10:12:03 |         MASTER-OAFA | (21h 51m 23.07s , -68d 47m 44.8s) |   C |    60 | 14.9 |        
   19133 | 2021-05-01 10:13:23 |         MASTER-OAFA | (22h 12m 54.26s , -68d 46m 51.3s) |   C |    60 | 14.8 |        
   19212 | 2021-05-01 10:14:42 |         MASTER-OAFA | (22h 05m 41.15s , -66d 47m 20.2s) |   C |    60 | 14.5 |        
   19292 | 2021-05-01 10:16:02 |         MASTER-OAFA | (22h 25m 26.53s , -66d 46m 28.7s) |   C |    60 | 14.4 |        
   19372 | 2021-05-01 10:17:22 |         MASTER-OAFA | (21h 36m 03.40s , -70d 47m 11.1s) |   C |    60 | 14.1 |        
   19454 | 2021-05-01 10:18:43 |         MASTER-OAFA | (00h 24m 07.93s , -62d 48m 58.8s) |   C |    60 | 13.6 |        
   19533 | 2021-05-01 10:20:03 |         MASTER-OAFA | (21h 59m 33.86s , -70d 48m 23.1s) |   C |    60 | 13.9 |        
   19617 | 2021-05-01 10:21:27 |         MASTER-OAFA | (00h 41m 15.38s , -62d 47m 14.5s) |   C |    60 | 13.0 |        
   19696 | 2021-05-01 10:22:46 |         MASTER-OAFA | (23h 49m 56.89s , -62d 49m 01.6s) |   C |    60 | 13.3 |        
   19776 | 2021-05-01 10:24:06 |         MASTER-OAFA | (00h 07m 05.87s , -62d 47m 41.9s) |   C |    60 | 13.3 |        
   19856 | 2021-05-01 10:25:26 |         MASTER-OAFA | (23h 07m 02.85s , -62d 48m 22.9s) |   C |    60 | 13.7 |        
   19936 | 2021-05-01 10:26:46 |         MASTER-OAFA | (23h 24m 09.80s , -62d 47m 22.5s) |   C |    60 | 13.4 |        
   65613 | 2021-05-01 23:08:02 |         MASTER-OAFA | (01h 20m 44.81s , -63d 27m 13.9s) |   C |    60 | 17.2 |        
   66746 | 2021-05-01 23:26:56 |         MASTER-OAFA | (01h 20m 39.43s , -63d 26m 48.4s) |   C |    60 | 17.0 |        
   67619 | 2021-05-01 23:41:29 |         MASTER-OAFA | (02h 19m 56.57s , -68d 46m 03.5s) |   C |    60 | 13.2 |        
   67996 | 2021-05-01 23:47:45 |         MASTER-OAFA | (01h 20m 39.92s , -63d 27m 49.4s) |   C |    60 | 16.3 |        
   68624 | 2021-05-01 23:58:14 |         MASTER-OAFA | (02h 19m 42.46s , -68d 46m 45.4s) |   C |    60 | 12.2 |        
   69582 | 2021-05-02 00:14:12 |         MASTER-OAFA | (02h 19m 53.88s , -68d 47m 32.6s) |   C |    60 | 12.7 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


