# GCN_circulars

GRB_name: GRB210712A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30457
SUBJECT: GRB 210712A: Swift-XRT refined Analysis
DATE:    21/07/13 03:01:23 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

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

We have analysed 8.5 ks of XRT data for GRB 210712A (Sbarufatti et al.
GCN Circ. 30447), from 86 s to 44.8 ks after the  BAT trigger. The data
comprise 164 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. 30453).

The late-time light curve (from T0+5.4 ks) can be modelled with a
power-law decay with a decay index of alpha=1.06 (+0.10, -0.09).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.52 (+/-0.06). The
best-fitting absorption column is  1.10 (+0.22, -0.21) x 10^21 cm^-2,
consistent with the Galactic value of 8.9 x 10^20 cm^-2 (Willingale et
al. 2013). The PC mode spectrum has a photon index of 1.98 (+0.13,
-0.09) 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 3.3 x 10^-11 (4.0 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      8.9 (+2.9, -0.0) x 10^20 cm^-2
Galactic foreground: 8.9 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.98 (+0.13, -0.09)

If the light curve continues to decay with a power-law decay index of
1.06, the count rate at T+24 hours will be 0.015 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.9 x
10^-13 (5.9 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/01059881.

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


GRB_name: GRB210712A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30460
SUBJECT: GRB 210712A: Swift-BAT refined analysis
DATE:    21/07/13 14:15:12 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm@nsf.gov>

T. N. Ukwatta (LANL), 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), T. Sakamoto (AGU), B. Sbarufatti (PSU),
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 210712A (trigger #1059881)
(Sbarufatti, et al., GCN Circ. 30447).  The BAT ground-calculated position is
RA, Dec = 97.322, -35.376 deg which is 
  RA(J2000)  =  06h 29m 17.3s 
  Dec(J2000) = -35d 22' 32.2" 
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 71%.

The mask-weighted light curve shows a series of peaks.  The first is from roughly
T-40 to T-30.  Then the strongest peak is from T-5 to T+15.  This is followed by a 
string of weaker peaks from T+20 to T+120.  The spacecraft slewed away from 
the burst location by T+700 sec.   T90 (15-350 keV) is 136.41 +- 63.58 sec 
(estimated error including systematics).

The time-averaged spectrum from -39.76 to 174.18 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.00 +- 0.53, 
and Epeak of 51.8 +- 11.6 keV (chi squared 70.95 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 3.0 +- 0.3 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+0.09 sec in the 15-150 keV band is
2.3 +- 0.3 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.85 +- 0.11 (chi squared 80.11 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/1059881/BA/


GRB_name: GRB210715B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30464
SUBJECT: GRB 210715B: DDOTI Upper Limits on the Afterglow
DATE:    21/07/15 19:22:06 GMT
FROM:    Kin O. C. L. Mendoza at Instituto de Astronoma, UNAM  <koclopez@astro.unam.mx>

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

We observed the field of the Fermi - GBM event GRB 210715.39 (Fermi
Collaboration, GCN Circ. 30463) with the DDOTI wide-field imager at the
Observatorio AstronÃ³mico Nacional on Sierra San Pedro Martir (
http://ddoti.astroscu.unam.mx) from 2021-07-15 09:34:11 to 11:26:28 UTC
(16.81 to 129.1 minutes after the trigger).


We observed a region of 20.4 degrees in RA by 20.4 degrees in declination,
with a 3 x 2 grid, centered on the Fermi GBM Final Position RA:  292.63,
DEC: +15.12 (J2000 degrees). This region contains 6 instrumental fields or
about 400 square degrees. We obtained 16 minutes of exposure per
instrumental field in the w filter. We obtained AB photometry by
calibration against the APASS catalog.


Comparing to the Pan-STARRS DR1 catalog, we detect no uncatalogued point
sources to a 10-sigma limiting magnitude of w = 19.2 - 19.6

We thank the staff of the Observatorio AstronÃ³mico Nacional in San Pedro
Martir.


GRB_name: GRB210704A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30465
SUBJECT: GRB 210704A: Zeiss-1000/SAO-RAS optical observations
DATE:    21/07/17 14:02:10 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

A. Volnova (IKI), A. Moskvitin (SAO RAS),  A. Pozanenko (IKI), N. Pankov 
(IKI, HSE), S. Belkin (IKI, HSE)  report on behalf of GRB IKI FuN:

We observed GRB 210704A  (Ursi et al., GCN 30372; Berretta et al., GCN 
30375; Prasad et al., GCN 30378; D'Ai et al., GCN 30379; Malacaria et 
al., GCN 30380; Ridnaia et al., GCN 30388)  with Zeiss-1000 telescope of 
SAO RAS observatory on 2021-07-11 and  2021-07-13.    We marginally 
detect the optical afterglow (Kim et al., GCN 30384; D'Avanzo et al., 
GCN 30385; Troja et al., GCN 30390; Kann et al., GCN 30391, 30401; Sun 
et al., GCN 30411; D'Avanzo et al., GCN 30432; Rastinejad  et al., GCN 
30433;  Watson et al., GCN 30436; Pankov et al., GCN 30440; Troja et 
al., GCN 30442; Kann et al., GCN 30443; Fong et al., GCN 30445; O'Connor 
et al., GCN  30451).

Preliminary photometry of the afterglow is following

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

2021-07-11 18:38:22   6.98262 R      12*300  23.1    0.3   23.2
2021-07-13 18:16:08   8.94635 R      24*300  23.8   S/N=2  23.5

The photometry is based on nearby USNO_B-1.0 stars
USNO_B-1.0_id R2
1471-0248922 16.31
1471-0248878 17.04


GRB_name: GRB210714A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30467
SUBJECT: Konus-Wind detection of GRB 210714A
DATE:    21/07/18 14:11:31 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:

GRB 210714A (Fermi-GBM trigger 647942198 / MASTER optical afterglow  detection: Lipunov et al., GCN 30466)
triggered Konus-Wind (KW) at T0=28598.602 s UT (07:56:38.602).

The burst light curve shows a bright, FRED-like pulse
which starts at ~T0-2.5 s, and has a total duration of ~80 s.
The emission is seen up to ~15 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210714_T28598/

As observed by Konus-Wind, the burst had
a fluence of (9.6 Â± 0.8)x10^-5 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 1.664 s,
of (1.07 Â± 0.10)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+46.848 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.25 (-0.20,+0.49),
the high energy photon index beta = -1.83 (-0.06,+0.05),
the peak energy Ep = 145 (-60,+81) keV,
chi2 = 101/97 dof.

The spectrum near the peak count rate (measured from T0+0.256
to T0+5.888 s) is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.01 (-0.30,+0.27),
the high energy photon index beta = -1.91 (-0.05,+0.04),
the peak energy Ep = 104 (-23,+39) keV,
chi2 = 111/97 dof.

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


GRB_name: GRB210719A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30472
SUBJECT: GRB 210719A: GECAM detection
DATE:    21/07/20 16:01:57 GMT
FROM:    Shenglun Xie at IHEP  <xiesl@ihep.ac.cn>

X. L. Zhang, W. C. Xue, S. Xiao, S. L. Xiong, X. Y. Zhao, X. Y. Song,
C. Cai, Y. Huang, S. L. Xie, J. C. Liu, C. Y. Li, Y. Q. Zhang,  Y. Zhao, 
Z. W. Guo, C. Zheng, 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, 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 in-flight by a long
burst, GRB 210719A, at 2021-07-19T02:24:59.500 UTC (denoted as T0).

According to the GECAM-B light curves in about 15-3500 keV, 
this burst mainly consists of multiple pulses with a duration about 400 s.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/LC_2021-07-19T02_24_59.500.png

GECAM-B localized this burst to the following position (J2000):
Ra: 82.64 deg
Dec: 51.02 deg
Err: 5.16 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 location map could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/tn210719_022608_location.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: GRB210722A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30475
SUBJECT: GRB 210722A: Swift detection of a burst with a bright optical counterpart
DATE:    21/07/22 21:13:43 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

P. D'Avanzo (INAF-OAB), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), M. J. Moss (GWU),
D. M. Palmer (LANL) and A. Tohuvavohu (U Toronto) report on behalf of
the Neil Gehrels Swift Observatory Team:

At 20:54:42 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210722A (trigger=1061223).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 27.023, -6.354 which is 
   RA(J2000) = 01h 48m 06s
   Dec(J2000) = -06d 21' 14"
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 30 sec.  The peak count rate
was ~1500 counts/sec (15-350 keV), at ~0 sec after the trigger. 

Using promptly downlinked XRT data we find an uncatalogued X-ray source located
at RA, Dec 27.028, -6.345 which is equivalent to:
   RA(J2000)  = +01h 48m 06.84
   Dec(J2000) = -06d 20' 42.7"
with an uncertainty of 5.0 arcseconds (radius, 90% containment). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 94 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
RA(J2000) = 01:48:07.27 = 27.03028
DEC(J2000) = -06:20:49.8 = -6.34718
with a 90%-confidence error radius of about 0.74 arc sec. This position is 9.6
arc sec. from the center of the XRT error circle. The estimated magnitude is
14.37 with a 1-sigma error of about 0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.027. 

Burst Advocate for this burst is P. D'Avanzo (paolo.davanzo 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: GRB210722A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30476
SUBJECT: GRB 210722A: Nanshan/NEXT optical afterglow observations
DATE:    21/07/22 21:58:22 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

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

We observed the field of GRB 210722A (D'Avanzo et al., GCN 30475) using 
the NEXT-0.6m telescope located at Nanshan, Xinjiang, China. We obtained 
a series of 40 s, 60 s, 90 s frames in the Sloan r-band, starting at 
20:56:45 UT on 2021-07-22, i.e., 123 s after the BAT trigger, among 
which part of the frames are useless due to the cloudy weather.

An uncatalogued optical transient is detected at the Swift/UVOT position 
(D'Avanzo et al., GCN 30475) with varying brightness, and thus confirms 
it as the optical afterglow of the burst. Preliminary analysis of the 
beginning photometry is as follows:

Tmid-T0(sec)  Mag    MagErr
143               14.33    0.01
361               13.94    0.01
452               14.01    0.01

All magnitudes are calibrated with the nearby PS1 field.


GRB_name: GRB210702A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30477
SUBJECT: GRB 210702A: ATCA detection of radio rebrightening
DATE:    21/07/22 22:42:20 GMT
FROM:    Tanmoy Laskar at U of Bath  <tanmoylaskar@gmail.com>

T. Laskar (U. of Bath) and S. Bhandari (CSIRO) report on behalf of a larger
collaboration:

"Following the initial detection of the radio counterpart of GRB 210702A
(Lien et al., GCN 30351) with the Australia Telescope Compact Array (ATCA)
on 2021 July 06, 3.50 days after the burst (Laskar et al., GCN 30424), we
have been monitoring this source with ATCA at 5.5, 9.0, 16.7, 21.2, and 34
GHz. The 34 GHz radio counterpart was observed to fade, until observations
taken on 2021 July 13 indicated a non-detection with map rms ~ 60 uJy at a
mid-time of 10.3 days after the burst.

We observed GRB 210702A with ATCA again at the above frequencies beginning
on 2021 July 21 07:00 UTC with the array in a hybrid (H168) configuration.
Preliminary analysis reveals a strong (> 10 sigma) detection at 34 GHz with
a flux density of ~ 0.7 mJy at a mid-time of 18.5 days after the burst,
implying a significant rebrightening of the radio afterglow. Similar
rebrightening is observed at 21.2 and 16.7 GHz.

Detailed analysis is ongoing and further observations are planned. We thank
the CSIRO staff for approving and scheduling these observations.

The Australia Telescope Compact Array is part of the Australia Telescope
National Facility which is funded by the Australian Government for
operation as a National Facility managed by CSIRO. We acknowledge the
Gomeroi people as the traditional owners of the Observatory site."


GRB_name: GRB210722A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30478
SUBJECT: GRB 210722A: Assy optical detection
DATE:    21/07/22 22:49:40 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

N. Pankov (HSE, IKI), M. Krugov (FAI), A. Pozanenko (IKI),  V. Kim (FAI, 
Pulkovo Observatory), S. Belkin (IKI) report on behalf of GRB IKI FuN:

We observed the field of  GRB 210722A  (D'Avanzo et al., GCN 30475) with 
AZT-20 telescope of Assy-Turgen observatory starting on 2021-07-22 (UT) 
21:42:07. We obtained 30 frames in r' - filter before a twilight.

We clearly detect the bright optical afterglow (D'Avanzo et al., GCN 
30475; Zhu et al., GCN 30476) in coordinates of 01:48:07.27 
-06:20:50.00 with accuracy of 0.1 arcsec in both coordinates. The 
coordinates are coincides with UVOT coordinates (D'Avanzo et al., GCN 30475)

Preliminary photometry of the optical afterglow in the first image of 60 
s exposure is following

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

2021-07-22 21:42:07 0.03293     1*60    r'      16.20 0.03  21.1


The photometry is based on the nearby PS1 stars.


GRB_name: GRB210702A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30479
SUBJECT: GRB 210702A: ALMA detection of mm-band rebrightening
DATE:    21/07/22 22:50:41 GMT
FROM:    Tanmoy Laskar at U of Bath  <tanmoylaskar@gmail.com>

T. Laskar (U. of Bath) reports on behalf of a larger collaboration:

"Following the initial detection of the mm counterpart of GRB 210702A (Lien
et al., GCN 30351) with the Atacama Large Millimeter/Submillimeter Array
(ALMA) on 2021 July 03, 26 h after the burst (Laskar & Perley, GCN 30423),
we have been monitoring this source with ALMA at 97.5 GHz. The mm-band
counterpart was observed to fade to a flux density of ~ 0.3 mJy in
observations taken on 2021 July 11 at a mid-time of 8.3 days after the
burst.

We observed GRB 210702A with ALMA again beginning on 2021 July 20 21:02
UTC. Preliminary analysis reveals a strong (~ 50 sigma) detection at 97.5
GHz with a flux density of ~ 0.8 mJy at a mid-time of 18.1 days after the
burst, implying a significant rebrightening of the mm-band afterglow,
contemporaneous to the radio rebrightening observed at 34, 21.2, and 16.7
GHz with ATCA (Laskar & Bhandari, GCN 30477). Further observations are
planned.

We thank the JAO staff, AoD, P2G, and the entire ALMA team for their help
with these observations."


GRB_name: GRB210722A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30480
SUBJECT: Swift GRB 210722A: Global MASTER-Net observations report 
DATE:    21/07/23 00:11:36 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-Tavrida robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the Swift GRB 210722A ( P. D'Avanzo et al., GCN 30475) errorbox  11033 sec after notice time and 11204 sec after trigger time at 2021-07-23 00:01:26 UT, with upper limit up to  17.6 mag. The observations began at zenith distance = 68 deg. The sun  altitude  is -19.1 deg. 

The galactic latitude b = -65 deg., longitude l = 159 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1667717

We obtain a following upper limits.  

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

   11294 |      MASTER-Tavrida |   C |   180 | 17.6 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210722A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30481
SUBJECT: GRB 210722A: GIT optical detection and preliminary analysis
DATE:    21/07/23 13:44:05 GMT
FROM:    Harsh Kumar at Indian Inst of Tech,Bombay  <harshkosli13@gmail.com>

H. Kumar(IITB), S. Joharle (Fergusson College), J. Stanzin (IAO), V.
Bhalerao(IITB), G. C. Anupama(IIA), S. Barway(IIA) report on behalf of the GIT
team:

We observed GRB 210722A detected by Swift Burst Alert Telescope (P.
D'Avanzo et al., GCN #30475) and optical afterglow detected by P. D'Avanzo
et al., GCN #30475; Z.P. Zhu et al., GCN #30476; N. Pankov et al., GCN
#30477; with 0.7m GROWTH-India Telescope (GIT). We obtained multiple
exposures in the g', r' filters. The image depth was shallower than usual
due to weather conditions. We clearly detected the afterglow in our images
at R.A.= 1:48:07.29, DEC.= -6:20:49.85, which agrees with the swift UVOT
position (GCN #30475). The photometric results follow as:

------------------------------------------------------------------------

T_start - T0 (days) | Exposure (sec) | Filter | Magnitude (AB)| Notes |

------------------------------------------------------------------------

 0.014938 | 100  | g' | 15.95 +/- 0.23 | Low significance detection

 0.012057 | 100  | r' | 15.11 +/- 0.08 |

 0.032546 | 4x100 | r' | 16.34 +/- 0.08 | Stacked image

 0.050742 | 100  | r' | 16.81 +/- 0.19 |

 0.053035 | 100  | r' | 16.88 +/- 0.07 |

 ------------------------------------------------------------------------

Based on our observations, we found that the GRB is decaying with a
power-law index of 1.14 +/- 0.03 in r' band. Our observations are in
agreement with magnitudes reported by Z.P. Zhu et al., GCN #30476, and N.
Pankov et al., GCN #30477. The magnitudes are calibrated against PanSTARRS
(Flewelling et al., 2018) and not corrected for Galactic extinction.

The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7-degree
field of view, set up by the Indian Institute of Astrophysics and the
Indian Institute of Technology Bombay with support from the Indo-US Science
and Technology Forum (IUSSTF) and the Science and Engineering Research
Board (SERB) of the Department of Science and Technology (DST), Government
of India (https://sites.google.com/view/growthindia/). It is located at the
Indian Astronomical Observatory (Hanle), operated by the Indian Institute
of Astrophysics (IIA).


GRB_name: GRB210722A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30482
SUBJECT: GRB 210722A: Swift/UVOT Detection
DATE:    21/07/23 13:46:11 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M. H. Siegel (PSU) and P. D'Avanzo (INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210722A
94 s after the BAT trigger (D'Avanzo et al., GCN Circ. 30475).
A source consistent with the XRT position is detected in the initial UVOT exposures.

The preliminary UVOT position is:
  RA  (J2000) =  01:48:07.28 =  27.03033 (deg.)
  Dec (J2000) = -06:20:49.7  =  -6.34713 (deg.)
with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence).

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               94          244          147         14.31 +/- 0.02
v                  637          656           19         14.52 +/- 0.06
b                  563          583           20         14.65 +/- 0.04
u                  308          557          246         13.68 +/- 0.02
w1                 686          705           20         14.08 +/- 0.06
w2                4908         4971           62         17.08 +/- 0.14

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.027 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210722A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30483
SUBJECT: GRB 210722A: Swift-XRT refined Analysis
DATE:    21/07/23 14:27:18 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), J. D. Gropp (PSU), J.A. Kennea (PSU), A.
Tohuvavohu (U. Toronto) and P. D'Avanzo report on behalf of the
Swift-XRT team:

We have analysed 6.3 ks of XRT data for GRB 210722A (D'Avanzo et al.
GCN Circ. 30475), from 91 s to 47.1 ks after the  BAT trigger. The data
comprise 294 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. Using 3301 s of PC mode data and 8 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 =
27.03023, -6.34758 which is equivalent to:

RA (J2000): 01h 48m 07.26s
Dec(J2000): -06d 20' 51.3"

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

The late-time light curve (from T0+4.5 ks) can be modelled with a
power-law decay with a decay index of alpha=1.31 (+0.10, -0.09).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.20 (+/-0.05). The
best-fitting absorption column is  4.2 (+1.0, -0.9) x 10^20 cm^-2, in
excess of the Galactic value of 2.2 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.84 (+0.11, -0.10)
and a best-fitting absorption column of 3.5 (+2.4, -1.2) x 10^20 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.5 x 10^-11 (3.8 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      3.5 (+2.4, -1.2) x 10^20 cm^-2
Galactic foreground: 2.2 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.84 (+0.11, -0.10)

If the light curve continues to decay with a power-law decay index of
1.31, the count rate at T+24 hours will be 0.013 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.4 x
10^-13 (4.8 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/01061223.

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


GRB_name: GRB210722A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30484
SUBJECT: GRB 210722A: RATIR Optical Observations
DATE:    21/07/23 14:49:14 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 210722A (D'Avanzo, et al., GCN 30475) 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 2021/07 23.40 to 2021/07 23.48 UTC (12.43 to 14.36 hours
after the BAT trigger), obtaining a total of 1.22 hours exposure in the r
and i bands.

In comparison with the SDSS DR9 and 2MASS catalogs, we obtain the following
detections of the optical afterglow:

  r = 19.41 +/- 0.05
  i = 19.35 +/- 0.04

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: GRB210723A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30485
SUBJECT: GRB 210723A: Swift detection of a burst
DATE:    21/07/23 15:04:47 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),
N. J. Klingler (GSFC/UMBC/CRESSTII), N. P. M. Kuin (UCL-MSSL),
S. Laha (GSFC/UMBC/CRESST), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),
D. M. Palmer (LANL), M. H. Siegel (PSU) and A. Tohuvavohu (U Toronto)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 14:46:10 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210723A (trigger=1061284).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 121.726, -32.889 which is 
   RA(J2000) = 08h 06m 54s
   Dec(J2000) = -32d 53' 20"
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 50 sec.  The peak count rate
was ~2200 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 14:47:40.4 UT, 89.6 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 121.72157,
-32.88624 which is equivalent to:
   RA(J2000)  = 08h 06m 53.18s
   Dec(J2000) = -32d 53' 10.5"
with an uncertainty of 7.0 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 7.70
x 10^21 cm^-2 (Willingale et al. 2013). 

The initial flux in the 2.5 s image was 3.04e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 99 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. Because of the density of catalogued stars, further
analysis is required to report an upper limit for any afterglow in the
sub-image. The 8'x8' region for the list of sources generated on-board covers
100% of the XRT error circle. Because of the density of catalogued stars,
further analysis is required to report an upper limit for any afterglow in the
region. No correction has been made for the large, but uncertain, extinction
expected. 

Although the data from this burst are consistent with a classical long
GRB, we note that this source is close to the Galactic plane 
(lat = -0.34 degrees) which raises the possibility that this is
a Galactic transient.  If further analysis determines that to be
the case, we would name the object Swift J0806.9-3253 . 

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: GRB210723A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30486
SUBJECT: GRB 210723A: Prompt enhanced Swift-XRT position
DATE:    21/07/23 15:23:33 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

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

Using  promptly downlinked XRT event data for GRB 210723A, we find an
enhanced XRT position of the afterglow: RA, Dec: 121.7213, -32.8851
which is equivalent to:
   RA (J2000)  = 08 06 53.12
   Dec (J2000) = -32 53 06.4
with an uncertainty of 1.9 arcseconds (radius, 90% confidence).
Analysis of the promptly available data is online at
http://www.swift.ac.uk/sper/1061284.

Position enhancement is is described by Goad et al. (2007, A&A, 476,
1401) and Evans et al. (2009, MNRAS, 397, 1177).

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


GRB_name: GRB210722A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30487
SUBJECT: GRB 210722A: Redshift from OSIRIS/GTC
DATE:    21/07/23 17:50:29 GMT
FROM:    C. C. Thoene at HETH/IAA-CSIC  <christina.thoene@gmail.com>

C. C. Thoene (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC,
DARK/NBI),  D. A. Kann, M. Blazek, J. F. Agui Fernandez (all
HETH/IAA-CSIC), J. P. U Fynbo (DAWN/NBI), L. Izzo (DARK/NBI), N. R. Tanvir
(U. Leicester) and N. Castro (GTC) report:

We obtained spectroscopy of the afterglow of GRB 210722A (Dâ€™Avanzo et al.
GCN #30475, Page et al. GCN #30483, Zhu et al. GCN #30476) with OSIRIS
mounted on the 10.4 m GTC telescope at the Roque de los Muchachos
observatory (La Palma, Spain). Observations started at 05:02:09 UT with a
mid-time of 05:17:30 UT (8.38 hr after the burst) and consisted of 2x900s
spectra taken with grism R1000B, which covers the spectral range between
3700 and 7800 AA. We also obtained an acquisition image of 60s in r'-band
at 04:58:25 UT. Observing conditions were rather bad with a seeing of 1.7
arcsec and taken during morning twilight.

We detect several weak absorption lines, consistent with the MgII doublet,
FeII 2344, 2374, 2383, 2587 and 2600 at a common redshift of z=1.145. The
lines are in the weakest 1.7% of the average GRB absorption line strength
(de Ugarte Postigo et al. 2012, A&A 548, 11). The detection of the
afterglow in all UVOT filters (Siegel et al. GCN #30482) is consistent with
this redshift.

The acquisition image shows the afterglow to be râ€™ = 18.92 +/- 0.03
compared to 7 SDSS field stars.


GRB_name: GRB210722A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30488
SUBJECT: GRB 210722A: Kitab optical observations, light curve
DATE:    21/07/23 17:59:25 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

N. Pankov (IKI, HSE), A. Zhornichenko (KIAM),  A. Pozanenko (IKI), V. 
Agletdinov (KIAM),  M. Krugov (FAI), V. Kim (FAI), S. Belkin (IKI), Sh. 
Ehgamberdiev (UBAI) report on behalf of IKI-GRB-FuN:

We observed the field of  GRB 210722A  (D'Avanzo et al., GCN 30475) with 
Kitab-ISON RC-36  telescope in Clear filter.  Observation started on 
July, 22  (UT) 21:31:44 and ended on July, 22  (UT) 23:20:06. We clearly 
detect the bright optical afterglow (D'Avanzo et al., GCN  30475; Zhu et 
al., GCN 30476; Pankov et al., GCN 30478; Lipunov  et al., GCN  30480; 
Kumar et al., GCN  30481; Siegel et al., GCN  30421; Butler et al., GCN 
  30484).
Preliminary photometry of the first and latest combined images are following


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

2021-07-22  21:31:44 0.02572   5*60  CR      16.00  0.15   18.4
2021-07-22  23:13:54 0.09667   7*60  CR      17.33  0.12   19.0

The photometry is based on nearby USNO-B1.0 stars, R2 magnitude.
USNO-B1.0_id R2
USNO_B10-0836-00016699
USNO_B10-0836-00016715

We approximate the light curve by single PL model with power law index 
of -1.1 which is corroborating with PL index reported by Kumar et al. 
(GCN  30481).  The light curve of our observations in Assy (Pankov et 
al., GCN 30478) and Kitab observatory can be found at

http://grb.rssi.ru/GRB210722A/GRB210722A_LC.jpeg


GRB_name: GRB210722A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30489
SUBJECT: GRB 210722A: Swift-BAT refined analysis
DATE:    21/07/23 20:37:20 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

S. D. Barthelmy (GSFC), P. D'Avanzo (INAF-OAB)
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 210722A (trigger #1061223)
(D'Avanzo et al., GCN Circ. 30475).  The BAT ground-calculated position is
RA, Dec = 27.031, -6.347 deg which is
   RA(J2000)  =  01h 48m 07.4s
   Dec(J2000) = -06d 20' 49.9"
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 43%.

The mask-weighted light curve shows a single-peaked structure that
starts at ~T-5 s, peaks at ~T0, and ends at ~T+30 s, with
some weak tail emission that lasts until ~T+60 s. T90 (15-350 keV)
is 50.20 +- 10.54 sec (estimated error including systematics).

The time-averaged spectrum from T-4.40 to T+59.59 sec is best fit by
a simple power-law model.  The power law index of the time-averaged
spectrum is 1.62 +- 0.14.  The fluence in the 15-150 keV band
is 2.5 +- 0.2 x 10^-06 erg/cm2. The 1-sec peak photon flux measured
from T+1.00 sec in the 15-150 keV band is 2.2 +- 0.5 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/1061223/BA/


GRB_name: GRB210722A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30490
SUBJECT: GRB 210722A: Fermi GBM observation
DATE:    21/07/23 21:29:26 GMT
FROM:    Joshua Wood at MSFC/Fermi-GBM  <joshua.r.wood@nasa.gov>

J. Wood (NASA/MSFC)
reports on behalf of the Fermi GBM Team:

"At 20:54:40.87 UT on 22 July 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210722A (trigger 648680085 / 210722871)
which was also detected by the Swift/BAT and Swift/XRT (P. D'Avanzo et al. 2021, GCN 30475).

The GBM on-ground location is consistent with the Swift position.

The GBM light curve consists of a single peak
with a duration (T90) of about 62 s (50-300 keV).
The time-averaged spectrum from T0-1.5 s to T0+62 s is
well fit by a power law function with an exponential
high-energy cutoff.  The power law index is -1.1 +/- 0.1 and
the cutoff energy, parameterized as Epeak, is 160 +/- 30 keV

The event fluence (10-1000 keV) in this time interval is
(5.8 +/- 0.6)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+2.3 s in the 10-1000 keV band
is 4.0 +/- 0.3 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: GRB210723A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30491
SUBJECT: Swift GRB 210723A: Global MASTER-Net observations report 
DATE:    21/07/23 23:16:55 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 210723A ( T. Sbarrato et al., GCN 30485) errorbox  29771 sec after notice time and 29801 sec after trigger time at 2021-07-23 23:02:52 UT, with upper limit up to  15.3 mag. Observations started at twilight.  The observations began at zenith distance = 80 deg. The sun  altitude  is -14.6 deg. 

The galactic latitude b = -0 deg., longitude l = 251 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1668344

We obtain a following upper limits.  

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

   29891 |         MASTER-OAFA |   C |   180 | 15.3 |        
   30091 |         MASTER-OAFA |   C |   180 | 14.7 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210722A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30492
SUBJECT: GRB 210722A: D50 optical detection
DATE:    21/07/24 08:40:09 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 210722A (D'Avanzo et al., GCN
30475; Page et a., GCN 30483; Barthelmy et al. GCN 30489; and Wood, GCN
30490) with the D50 telescope of the Astronomical Institute Ondrejov, near
Prague, Czech Republic. We performed a set of 35x 60s exposures in SDSS-i'
filter on July 24 from 1:20 to 2:01 UT.

The optical afterglow (Zhu et al., GCN 30476; Pankov et al., GCN 30478 &
30488; Kumar et al., GCN 30481; Butler et al., GCN 30484; and Thoene et
al., GCN 30487) is weakly detected in the overall combined image with the
exposure mean time 28.9h after trigger. The Atlas-calibrated magnitude of
the object is i' = 19.8 +/- 0.4.


GRB_name: GRB210723A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30493
SUBJECT: GRB 210723A: Swift-XRT refined Analysis
DATE:    21/07/24 11:06:33 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.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU),
J.P. Osborne (U. Leicester) and T. Sbarrato report on behalf of the
Swift-XRT team:

We have analysed 6.3 ks of XRT data for GRB 210723A (Sbarrato et al.
GCN Circ. 30485), from 79 s to 57.3 ks after the  BAT trigger. The data
comprise 267 s in Windowed Timing (WT) mode (the first 9 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. Using 3236 s of PC mode data and 6 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 = 121.72115, -32.88570
which is equivalent to:

RA (J2000): 08h 06m 53.08s
Dec(J2000): -32d 53' 08.5"

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

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=2.45 (+/-0.15). At T+154 s  the decay
flattens to an alpha of 1.67 (+/-0.09) before breaking again at T+959 s
to a final decay with index alpha=1.04 (+0.09, -0.23).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.75 (+0.11, -0.10). The
best-fitting absorption column is  1.26 (+0.14, -0.13) x 10^22 cm^-2,
in excess of the Galactic value of 7.7 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.71 (+0.26, -0.25)
and a best-fitting absorption column of 1.6 (+0.4, -0.3) x 10^22 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 6.5 x 10^-11 (1.1 x 10^-10) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.6 (+0.4, -0.3) x 10^22 cm^-2
Galactic foreground: 7.7 x 10^21 cm^-2
Excess significance: 4.1 sigma
Photon index:      1.71 (+0.26, -0.25)

If the light curve continues to decay with a power-law decay index of
1.04, the count rate at T+24 hours will be 7.0 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.6 x
10^-13 (7.7 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/01061284.

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


GRB_name: GRB210722A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30494
SUBJECT: GRB 210722A: continued Assy optical observations
DATE:    21/07/24 12:10:35 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

N. Pankov (HSE, IKI), V. Kim (FAI, Pulkovo Observatory), A. Pozanenko 
(IKI),  M. Krugov (FAI),  S. Belkin (IKI) report on behalf of GRB IKI FuN:

We continue observations of of the field of GRB 210722A  (D'Avanzo et 
al., GCN 30475;  Page et al., GCN 30483; Barthelmy et al. GCN 30489; 
Wood et al., GCN30490)  with AZT-20 telescope of Assy-Turgen 
observatory. We obtained several frames  in r' - filter starting on 
21-07-23 (UT) 21:34:39. We clearly detect the bright optical afterglow 
(D'Avanzo et al., GCN 30475; Zhu et al., GCN 30476; Pankov et al., GCN 
30478 & 30488; Kumar et al., GCN 30481; Butler et al., GCN 30484; 
Thoene et al., GCN 30487; Jelinek et al., GCN 30492).

Preliminary photometry of the afterglow in the stacked image  is following

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

2021-07-23 21:34:39 1.03677    26*60    r'      20.37 0.07  22.5

The photometry is based on the nearby PS1 stars.

The light curve can still be approximated by a single power law with a 
an index of -1.1.


GRB_name: GRB210723A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30495
SUBJECT: GRB 210723A: Swift-BAT refined analysis
DATE:    21/07/24 20:28:49 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

H. A. Krimm (NSF), S. D. Barthelmy (GSFC),

S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),

C. B. Markwardt (GSFC), 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-239 to T+861 sec from the recent telemetry
downlink,

we report further analysis of BAT GRB 210723A (trigger #1061284)

(Sbarrato et al., GCN Circ. 30485).  The BAT ground-calculated position is

RA, Dec = 121.723, -32.893 deg which is

   RA(J2000)  =  08h 06m 53.4s

   Dec(J2000) = -32d 53' 35.8"

with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).

The partial coding was 77%.



The mask-weighted light curve shows a single-pulse structure that

starts at ~T-5 s, peaks at ~T0, and ends at ~T+65 s. T90 (15-350 keV)

is 48.54 +- 3.50 sec (estimated error including systematics).



The time-averaged spectrum from T-4.59 to T+66.64 sec is best fit

by a power law with an exponential cutoff.  This fit gives a photon

index 0.85 +- 0.29, and Epeak of 88.2 +- 15.3 keV (chi squared 54.48

for 52 d.o.f.).  For this model the total fluence in the 15-150 keV band

is 5.3 +- 0.2 x 10^-6 erg/cm2 and the 1-sec peak flux measured from

T+2.68 sec in the 15-150 keV band is 3.1 +- 0.3 ph/cm2/sec.

A fit to a simple power law gives a photon index of 1.60 +- 0.06 (chi

squared 75.55 for 53 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/1061284/BA/


GRB_name: GRB210724A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30497
SUBJECT: GRB 210724A: Swift detection of a burst
DATE:    21/07/24 20:37:28 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

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

At 20:14:09 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210724A (trigger=1061482).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 227.407d, -6.274d which is 
   RA(J2000) = 15h 09m 38s
   Dec(J2000) = -06d 16' 27"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty). Due to a telemetry outage the BAT lightcurve is
not immediately available.  However, the trigger information indicates
a duration of at least 4 seconds. 

The XRT began observing the field at 20:17:09.0 UT, 179.8 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 227.4118,
-6.2911 which is equivalent to:
   RA(J2000)  = 15h 09m 38.83s
   Dec(J2000) = -06d 17' 27.8"
with an uncertainty of 1.9 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 8.23
x 10^20 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 124 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
0.097. 

Burst Advocate for this burst is P. D'Avanzo (paolo.davanzo 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: GRB210724A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30498
SUBJECT: GRB210724A: MeerLICHT upper limits
DATE:    21/07/24 22:56:14 GMT
FROM:    Simon de Wet at University of Cape Town  <dwtsim002@myuct.ac.za>

S. de Wet (UCT), P.J. Groot (Radboud/UCT/SAAO), A.J. Levan (Radboud),
P.M. Vreeswijk (Radboud), report on behalf of the MeerLICHT consortium:

Following the detection of GRB210724A by Swift and its X-ray
counterpart (D'Avanzo et al., GCN30497), the 0.6m MeerLICHT telescope,
located at Sutherland, South Africa obtained a repeating series of
60s images in the q,u,q,g,q,r,q,i,q,z bands. Observations began at
2021-07-24, 20:25:18.02 UT, 11 minutes after the Swift detection,
and 2 minutes after the distribution of the BAT alert, and continued
untill 21:27:36 UT.

We detect no optical afterglow at the XRT position (DAvanzo et al.
GCN30497) in our first u,g,q,r,i,z exposures to 5-sigma limiting
magnitudes of:

u > 18.59 at 20:27:37 UT
g > 19.40 at 20:31:01 UT
q > 19.77 at 20:25:49 UT
r > 19.38 at 20:34:31 UT
i > 19.26 at 20:37:45 UT
z > 18.14 at 20:59:12 UT

Full moon conditions limited the depth of our exposures.

We do note that an r=21.5 object is visible within the XRT localisation
in PanSTARRS imaging of the field, and is a plausible host galaxy.

MeerLICHT is built and run by a consortium consisting of Radboud
University, University of Cape Town, the South African Astronomical
Observatory, the University of Oxford, the University of Manchester
and the University of Amsterdam.
Disclaimer - University of Cape Town This email is subject to UCT policies and email disclaimer published on our website at http://www.uct.ac.za/main/email-disclaimer or obtainable from +27 21 650 9111. If this email is not related to the business of UCT, it is sent by the sender in an individual capacity. Please report security incidents or abuse via https://csirt.uct.ac.za/page/report-an-incident.php.


GRB_name: GRB210723A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30499
SUBJECT: GRB 210723A: Fermi GBM Observation
DATE:    21/07/25 01:23:27 GMT
FROM:    Suraj Poolakkil at UAH  <sp0076@uah.edu>

S. Lesage (UAH), B. Hristov (UAH) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

At 14:46:07 UT on 23 July 2021, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 210723A (trigger 648744372/210723615).
which was also detected by Swift BAT (T. Sbarrato et al. 2021, GCN 30485)
The Fermi GBM on-ground location is consistent with the Swift BAT position.

The angle from the Fermi LAT boresight is 94 degrees.

The GBM light curve consists of a single emission episode with a duration
(T90)
of about 43 s (10-1000 keV). The time-averaged spectrum
from T0+1.5 to T0+36.4 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.67 +/- 0.07 and the cutoff energy,
parameterized as Epeak, is 113 +/- 5 keV.

The event fluence (10-1000 keV) in this time interval is
(7.6 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1 s in the 10-1000 keV band is 4.7 +/- 0.3 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: GRB210725A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30501
SUBJECT: GRB 210725A: Swift detection of a burst
DATE:    21/07/25 04:07:21 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

M. G. Bernardini (INAF-OAB), P. D'Avanzo (INAF-OAB),
N. J. Klingler (GSFC/UMBC/CRESSTII), A. Y. Lien (GSFC/UMBC),
A. Melandri (INAF-OAB), D. M. Palmer (LANL) and T. Sbarrato (INAF-OAB)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 03:47:02 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210725A (trigger=1061511).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 215.363, -1.177 which is 
   RA(J2000) = 14h 21m 27s
   Dec(J2000) = -01d 10' 36"
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 10 sec.  The peak count rate
was ~1800 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 03:48:53.6 UT, 110.7 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 215.3742,
-1.1934 which is equivalent to:
   RA(J2000)  = 14h 21m 29.81s
   Dec(J2000) = -01d 11' 36.2"
with an uncertainty of 1.9 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 (4.09 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.9
(+2.81/-2.40) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 114 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 none of
the XRT error circle. 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 0.046. 

Burst Advocate for this burst is M. G. Bernardini (grazia.bernardini 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: GRB210725A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30503
SUBJECT: GRB 210725A: KAIT Optical Upper Limit
DATE:    21/07/25 05:20:35 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 210725A (Bernardini et al.,
GCN 30501) starting at 56 minutes after the burst. A total of
30x60s images were obtained in the clear (roughly R) filters.
We do not detect any optical afterglow candidate within the XRT
position error circle (Bernardini et al., GCN 30501), neither in
single image, nor in the co-add images. The typical limiting magnitude
of our single clear image is about 18.5 mag calibrated to the PS1 catalog.


GRB_name: GRB210722A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30504
SUBJECT: GRB 210722A: Nanshan/NEXT further optical observations
DATE:    21/07/25 07:56:29 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 continued to observe the field of GRB 210722A (D'Avanzo et al., GCN 
30475) using the NEXT-0.6m telescope located at Nanshan, Xinjiang, 
China. We obtained 15x200 s frames in the Sloan r-band, starting at 
20:41:20 UT on 2021-07-24, i.e., 1.99 days after the burst.

The previously reported optical afterglow (e.g., D'Avanzo et al., GCN 
30475; Zhu et al., GCN 30476) is not detected in our stacked image, down 
to a limiting magnitude of r~21.0, calibrated with the nearby PanSTARRS 
field.


GRB_name: GRB210722A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30505
SUBJECT: GRB 210722A: continued Assy optical observations
DATE:    21/07/25 08:13:48 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

V. Kim (FAI, Pulkovo Observatory), A. Pozanenko (IKI), N. Pankov (HSE, 
IKI),   M. Krugov (FAI),  S. Belkin (IKI) report on behalf of GRB IKI FuN:

We continue observations of of the field of GRB 210722A  (D'Avanzo et 
al., GCN 30475;  Page et al., GCN 30483; Barthelmy et al. GCN 30489; 
Wood et al., GCN30490)  with AZT-20 telescope of Assy-Turgen 
observatory. We obtained several frames  in r' - filter starting on 
21-07-24 (UT) 21:34:39. We clearly detect the bright optical afterglow 
(D'Avanzo et al., GCN 30475; Zhu et al., GCN 30476; Pankov et al., GCN 
30478, 30488, 30494; Kumar et al., GCN 30481; Butler et al., GCN 30484; 
Thoene et al., GCN 30487; Jelinek et al., GCN 30492; Fu et al., GCN  30504).

Preliminary photometry of the afterglow in the stacked image  is following

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

2021-07-24 20:56:07   n/d       42*60    r'     21.3  0.2   21.7

The photometry is based on the nearby PS1 stars.

The photometry is  still compatible with the single power law of the 
afterglow light curve.


GRB_name: GRB210723A
Detection_method: CALET
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30506
SUBJECT: GRB 210723A: CALET Gamma-Ray Burst Monitor detection
DATE:    21/07/25 10:03:08 GMT
FROM:    Valentin Pal'shin at AGU  <val@phys.aoyama.ac.jp>

Y. Asaoka (ICRR),
A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (AGU),
Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN),
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 long GRB 210723A (Swift detection: Sbarrato et al., GCN Circ. 30485,
Krimm and Barthelmy, GCN Circ. 30495; Fermi GBM Observation:
Lesage et al., GCN Circ. 30499;
https://gcn.gsfc.nasa.gov/other/210723A.gcn3) triggered the CALET Gamma-ray
Burst Monitor (CGBM) at 14:46:05.572 UTC on 23 July 2021
(http://cgbm.calet.jp/cgbm_trigger/flight/1311086521/index.html).
The burst signal was seen only by the SGM detector.

The burst light curve shows a single-pulse structure which starts
at T+0.9 sec, peaks at T+12.6 sec,and ends at T+22.0 sec.
The T90 and T50 durations measured by the SGM data are 17.2 +- 3.2 sec and
10.6 +- 3.2 sec (40-1000 keV), respectively.

The ground processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1311086521/

The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at the Waseda University.


GRB_name: GRB210725A
Detection_method: CALET
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30507
SUBJECT: GRB 210725A: CALET Gamma-Ray Burst Monitor detection
DATE:    21/07/25 10:59:46 GMT
FROM:    Valentin Pal'shin at AGU  <val@phys.aoyama.ac.jp>

S. Torii (Waseda U),
A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (AGU),
Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN),
Y. Asaoka (ICRR), 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 long GRB 210725A (Swift detection: Bernardini et al., GCN Circ. 30501;
https://gcn.gsfc.nasa.gov/other/210725A.gcn3) triggered the CALET
Gamma-ray Burst Monitor (CGBM) at 03:47:01.565 UTC on 25 July 2021
(http://cgbm.calet.jp/cgbm_trigger/flight/1311219774/index.html).
The burst signal was seen only by the SGM detector.

The burst light curve shows a single weak pulse which starts at T+1.4 sec,
peaks at T+1.5 sec,and ends at T+6.9 sec. The T90 and T50 durations
measured by the SGM data are 5.0 +- 0.7 sec and 3.0 +- 0.9 sec
(40-1000 keV), respectively.

The ground processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1311219774/

The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at the Waseda University.


GRB_name: GRB210725B
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30508
SUBJECT: GRB 210725B: Swift detection of a burst
DATE:    21/07/25 12:27:57 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

M. G. Bernardini (INAF-OAB), P. D'Avanzo (INAF-OAB),
J. A. Kennea (PSU), N. J. Klingler (GSFC/UMBC/CRESSTII),
F. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB),
D. M. Palmer (LANL), T. Sakamoto (AGU) and T. Sbarrato (INAF-OAB)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 12:00:48 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210725B (trigger=1061554).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 192.932, +17.125 which is 
   RA(J2000) = 12h 51m 44s
   Dec(J2000) = +17d 07' 30"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The immediately-available BAT light curve
(extending to T+8 seconds) shows a complex peak of at least 5 seconds
duration.  The peak count rate was ~1000 counts/sec (15-350 keV), 
at ~2 sec after the trigger. 

The XRT began observing the field at 12:02:18.8 UT, 90.9 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 192.9219,
17.1080 which is equivalent to:
   RA(J2000)  = 12h 51m 41.26s
   Dec(J2000) = +17d 06' 28.9"
with an uncertainty of 1.9 arcseconds (radius, 90% containment). This
location is 70 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. No
spectrum from the promptly downlinked event data is yet available to
determine the column density. 

UVOT took a finding chart exposure of 250 seconds with the U filter starting 91
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 19.2 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 18.0 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.023. 

Burst Advocate for this burst is M. G. Bernardini (grazia.bernardini 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: GRB210725A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30509
SUBJECT: GRB 210725A: MITSuME Akeno optical upper limits
DATE:    21/07/25 14:19:34 GMT
FROM:    Masafumi Niwano at Tokyo Institute of Tech  <niwano@hp.phys.titech.ac.jp>

M. Niwano, R. Hosokawa, K. L. Murata, N. Ito, H. Takamatsu, Y. Imai, R. 
Noto, S. Sato, M. Takaku, R. Yamaguchi, Y. Yatsu, and N. Kawai 
(TokyoTech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 210725A (Bernardini et al. GCN Circular 
#30501, WeiKang Zheng et al. GCN Circular #30503, S. Torii et al. GCN 
Circular #30507) with the optical three color (g', Rc, and Ic) CCD 
cameras attached to the MITSuME 50 cm telescope Akeno. The observation 
with a series of 60 sec exposures started at 2021-07-25 10:26:07 UT (6.7 
hours after Swift BAT trigger). We stacked the images with good 
conditions. We did not detect any uncatalogued sources within the XRT 
error region (Bernardini et al. GCN Circular #30501). We obtained the 
5-sigma limits of the stacked images as follows.

T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
6.7 2021-07-25 11:21:56.58 900 g'>18.6, Rc>18.9, Ic>18.4
------------------------------------------------------------------------------------------------
T-EXP: Total Exposure time

We used 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: GRB210725B
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30510
SUBJECT: GRB 210725B: Enhanced Swift-XRT position
DATE:    21/07/25 15:29:04 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 273 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 210725B, 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 = 192.92217, +17.10809 which is equivalent
to:

RA (J2000): 12h 51m 41.32s
Dec (J2000): +17d 06' 29.1"

with an uncertainty of 2.5 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: GRB210724A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30511
SUBJECT: GRB 210724A: Afterglow candidate from OSIRIS/GTC
DATE:    21/07/25 16:50:29 GMT
FROM:    Antonio de Ugarte Postigo at IAA-CSIC  <deugarte@iaa.es>

A. de Ugarte Postigo (HETH/IAA-CSIC,DARK/NBI), C. C. Thoene, D. A. Kann, M. Blazek, J. F. Agui Fernandez (all HETH/IAA-CSIC), J. P. U. Fynbo (DAWN/NBI), L. Izzo (DARK/NBI), N. R. Tanvir (U. Leicester), N. Castro-Rodriguez, and A. Marante (GRANTECAN, IAC) report:

We observed the field of GRB 210724A (D'Avanzo et al. GCN 30497) with OSIRIS mounted on the 10.4 m GTC telescope at  the Roque de los Muchachos observatory (La Palma, Spain). Observations started at 22:07 UT (1.88 hr after the burst). Observations were affected by strong calima and the full Moon, which resulted in bad transparency and very high background. In a series of short images in r', i' and z' bands we detect a new source, not present in the PanSTARRS catalogue images. The object is located at (J2000 +/- 0.5"):

RA: 15:09:39.44
Dec.: -06:17:26.0

This object had a magnitude of r' = 22.00 +/- 0.15 mag as compared to PanSTARRS field stars. We note that this source is within the early XRT alert error circles but outside the refined one (D'Avanzo et al. GCN 30497). There is no new source detected within this refined error circle. Due to the fact that this source is significantly brighter than the PanSTARRS limit, we propose it as the optical counterpart of GRB 210724A.


GRB_name: GRB210725B
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30512
SUBJECT: Swift GRB 210725B: Global MASTER-Net observations report 
DATE:    21/07/25 18:30:29 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-Tavrida robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the Swift GRB 210725B ( M. G. Bernardini et al., GCN 30508) errorbox  22581 sec after notice time and 22657 sec after trigger time at 2021-07-25 18:18:25 UT, with upper limit up to  16.5 mag. Observations started at twilight.  The observations began at zenith distance = 56 deg. The sun  altitude  is -10.3 deg. 

The galactic latitude b = 80 deg., longitude l = 307 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1669944

We obtain a following upper limits.  

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

   22747 |      MASTER-Tavrida |   C |   180 | 16.5 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210724A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30513
SUBJECT: GRB 210724A: Swift-BAT refined analysis
DATE:    21/07/25 19:43:26 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC),
P. D'Avanzo (INAF-OAB), H. A. Krimm (NSF),
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-240 to T+962 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 210724A (trigger #1061482)
(D'Avanzo et al., GCN Circ. 30497).  The BAT ground-calculated position is
RA, Dec = 227.425, -6.279 deg which is
   RA(J2000)  =  15h 09m 41.9s
   Dec(J2000) = -06d 16' 42.9"
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 34%.

The mask-weighted light curve shows a multi-peaked structure
that starts at ~T-40 s and ends at ~T+25 s. The main peak
occurs at ~T0. T90 (15-350 keV) is 50.57 +- 9.54 sec (estimated
error including systematics).

The time-averaged spectrum from T-38.55 to T+25.50 sec is best
fit by a simple power-law model.  The power law index of the
time-averaged  spectrum is 2.30 +- 0.28.  The fluence in the
15-150 keV band is 1.8 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak
photon flux measured from T-0.51 sec in the 15-150 keV band
is 2.5 +- 0.8 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/1061482/BA/


GRB_name: GRB210725A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30514
SUBJECT: GRB 210725A: Swift-BAT refined analysis
DATE:    21/07/25 20:06:04 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC),
M. G. Bernardini (INAF-OAB), H. A. Krimm (NSF),
S. Laha (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 210725A (trigger #1061511)
(Bernardini et al., GCN Circ. 30501).  The BAT ground-calculated position is
RA, Dec = 215.381, -1.177 deg which is
   RA(J2000)  =  14h 21m 31.4s
   Dec(J2000) = -01d 10' 37.2"
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 92%.

The mask-weighted light curve shows a multi-peaked structure that
starts at ~T0 and ends at ~T+60 s. The main peak occurs at ~T+1 s.
T90 (15-350 keV) is 53.54 +- 11.25 sec (estimated error including
systematics).

The time-averaged spectrum from T-0.82 to T+59.86 sec is best fit
by a simple power-law model.  The power law index of the time-averaged
spectrum is 1.42 +- 0.32.  The fluence in the 15-150 keV band
is 8.1 +- 1.2 x 10^-7 erg/cm2. The 1-sec peak photon flux measured
from T+1.01 sec in the 15-150 keV band is 1.0 +- 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/1061511/BA/


GRB_name: GRB210724A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30515
SUBJECT: GRB 210724A: Swift-XRT refined Analysis
DATE:    21/07/25 21:43:29 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), A. Tohuvavohu (U. Toronto), B.
Sbarufatti (PSU), D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L.
Page (U. Leicester) and P. D'Avanzo report on behalf of the Swift-XRT
team:

We have analysed 2.5 ks of XRT data for GRB 210724A (D'Avanzo et al.
GCN Circ. 30497), from 123 s to 84.6 ks after the  BAT trigger. The
data comprise 263 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. Using 331 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 =
227.41131, -6.29009 which is equivalent to:

RA (J2000): 15h 09m 38.72s
Dec(J2000): -06d 17' 24.3"

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

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.17 (+0.10, -0.09).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.48 (+/-0.08). The
best-fitting absorption column is  2.08 (+0.23, -0.22) x 10^21 cm^-2,
in excess of the Galactic value of 8.2 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 2.8 x 10^-11 (4.9 x 10^-11) erg
cm^-2 count^-1. 

A summary of the WT-mode spectrum is thus:
Total column:      2.08 (+0.23, -0.22) x 10^21 cm^-2
Galactic foreground: 8.2 x 10^20 cm^-2
Excess significance: 9.5 sigma
Photon index:      2.48 (+/-0.08)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01061482.

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


GRB_name: GRB210725B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30516
SUBJECT: GRB 210725B: Swift-BAT refined analysis
DATE:    21/07/25 21:48:44 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC),
M. G. Bernardini (INAF-OAB), J. R. Cummings (CPI),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (GSFC/UMBC), 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+400 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 210725B (trigger #1061554)
(Bernardini et al., GCN Circ. 30508).  The BAT ground-calculated position is
RA, Dec = 192.914, 17.130 deg which is
   RA(J2000)  =  12h 51m 39.3s
   Dec(J2000) = +17d 07' 48.5"
with an uncertainty of 2.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 98%.

The mask-weighted light curve shows a main pulse that starts at ~T0, peaks
at ~T+1 s, and ends at ~T+5 s. In addition, there are some weak emission
that starts at ~T-30 s and ends at ~T+15 s. T90 (15-350 keV) is
48.00 +- 22.63 sec (estimated error including systematics).

The time-averaged spectrum from T-31.46 to T+16.54 sec is best fit
by a simple power-law model.  The power law index of the time-averaged
spectrum is 1.16 +- 0.43.  The fluence in the 15-150 keV band is
4.9 +- 1.1 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from
T+0.97 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/1061554/BA/


GRB_name: GRB210725A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30517
SUBJECT: GRB 210725A: Swift-XRT refined Analysis
DATE:    21/07/26 00:09:08 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), B. Sbarufatti (PSU), D.N. Burrows (PSU), J. D. Gropp
(PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P.
Beardmore (U. Leicester) and M.G. Bernardini report on behalf of the
Swift-XRT team:

We have analysed 6.3 ks of XRT data for GRB 210725A (Bernardini et al.
GCN Circ. 30501), from 114 s to 64.8 ks after the  BAT trigger. The
data comprise 74 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. Using 1409 s of PC mode data and 2 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 =
215.37414, -1.19268 which is equivalent to:

RA (J2000): 14h 21m 29.79s
Dec(J2000): -01d 11' 33.6"

with an uncertainty of 1.9 arcsec (radius, 90% confidence).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.99 (+/-0.08).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.48 (+0.21, -0.19). The
best-fitting absorption column is  8.0 (+6.8, -3.9) x 10^20 cm^-2,
consistent with the Galactic value of 4.1 x 10^20 cm^-2 (Willingale et
al. 2013). 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:      8.0 (+6.8, -3.9) x 10^20 cm^-2
Galactic foreground: 4.1 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.48 (+0.21, -0.19)

If the light curve continues to decay with a power-law decay index of
1.99, the count rate at T+24 hours will be 1.2 x 10^-5 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.6 x
10^-16 (6.1 x 10^-16) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01061511.

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


GRB_name: GRB210724A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30518
SUBJECT: GRB 210724A: Zeiss-1000 of Koshka observatory, optical upper limit
DATE:    21/07/26 12:14:12 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

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

We observed the field of  GRB 210724A (D'Avanzo et al. GCN 30497) with 
Zeiss-1000 telescope of Koshka observatory starting on July 24 (UT) 
20:39:32. We do not detect any object XRT error circle (D'Avanzo et al. 
GCN 30497). We also not detect the object at the position of the 
afterglow candidate (Ugarte Postigo et al., GCN 30511).

Preliminary photometry of the field is following

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

2021-07-24 20:39:32   0.024919    R     21*60   n/d  n/d   18.6

The photometry is based on the nearby USNO-B1.0 stars
USNO-B1.0_id R2
USNO-B1.0_id R2
0837-0267865 15.24
0836-0268753 16.95
0837-0267827 15.54


GRB_name: GRB210725A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30519
SUBJECT: GRB 210725A: Fermi GBM detection
DATE:    21/07/26 16:48:00 GMT
FROM:    Suraj Poolakkil at UAH  <sp0076@uah.edu>

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

"At 03:47:03.54 UT on 25 July 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210725A (trigger 648877628 / 210725158)
which was also detected by the Swift/BAT (Bernardini et al. 2021, GCN
30501).
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 78
degrees.

The GBM light curve consists of a single peak followed by some
extended emission with a duration (T90) of about 47 s (50-300 keV).
The time-averaged spectrum from T0-1.02 s to T0+9.21 s
is best fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.37 +/- 0.22  and
the cutoff energy, parameterized as Epeak, is 460 +/- 104 keV.

The event fluence (10-1000 keV) in this time interval is
(3.14 +/- 0.35)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0.64 s in the 10-1000 keV band
is 2.0 +/- 0.2 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: GRB210725B
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30520
SUBJECT: GRB 210725B: Swift-XRT refined Analysis
DATE:    21/07/26 18:58:04 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

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

We have analysed 4.9 ks of XRT data for GRB 210725B (Bernardini et al.
GCN Circ. 30508), from 94 s to 107.1 ks after the  BAT trigger. The
data comprise 68 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. 30510).

The light curve can be modelled with a power-law decay with a decay
index of alpha=3.43 (+0.20, -0.18).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.77 (+0.29, -0.27). The
best-fitting absorption column is  6.6 (+2.7, -2.1) x 10^21 cm^-2, in
excess of the Galactic value of 2.0 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 4.5 x 10^-11 (6.7 x 10^-11) erg
cm^-2 count^-1. 

A summary of the WT-mode spectrum is thus:
Total column:      6.6 (+2.7, -2.1) x 10^21 cm^-2
Galactic foreground: 2.0 x 10^20 cm^-2
Excess significance: 5.2 sigma
Photon index:      1.77 (+0.29, -0.27)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01061554.

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


GRB_name: GRB210726A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30523
SUBJECT: GRB 210726A: Swift detection of a burst
DATE:    21/07/26 19:39:05 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

M. G. Bernardini (INAF-OAB), M. A. Baer (PSU), P. D'Avanzo (INAF-OAB),
J. A. Kennea (PSU), N. J. Klingler (GSFC/UMBC/CRESSTII),
S. Laha (GSFC/UMBC/CRESST), F. E. Marshall (NASA/GSFC),
A. Melandri (INAF-OAB), M. J. Moss (GWU), K. L. Page (U Leicester),
D. M. Palmer (LANL), M. H. Siegel (PSU) and A. Tohuvavohu (U Toronto)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 19:19:03 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210726A (trigger=1061687).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 193.342, +19.185 which is 
   RA(J2000) = 12h 53m 22s
   Dec(J2000) = +19d 11' 05"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a short spike with 
a tail with a total duration of about ~3 sec.  The peak count rate
was ~1500 counts/sec (15-350 keV), at ~0 sec after the trigger. 
This may be a short GRB. 

The XRT began observing the field at 19:20:03.6 UT, 60.0 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 193.2909,
19.1898 which is equivalent to:
   RA(J2000)  = 12h 53m 09.81s
   Dec(J2000) = +19d 11' 23.2"
with an uncertainty of 1.9 arcseconds (radius, 90% containment). This
location is 174 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 (1.73 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.4
(+2.93/-2.51) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 250 seconds with the U filter starting
276 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 none of the
XRT error circle. 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 18.0 mag. No correction has been made for the expected extinction
corresponding to E(B-V) of 0.020. 

Burst Advocate for this burst is M. G. Bernardini (grazia.bernardini 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: GRB210726A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30524
SUBJECT: GRB 210726A: Enhanced Swift-XRT position
DATE:    21/07/26 21:21:52 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 1692 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 210726A, 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 = 193.29093, +19.19030 which is equivalent
to:

RA (J2000): 12h 53m 9.82s
Dec (J2000): +19d 11' 25.1"

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: GRB210726A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30525
SUBJECT: GRB 210726A: CAHA 2.2m telescope optical limit
DATE:    21/07/26 22:25:14 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), A. Gardini and I. Hermelo (CAHA) on behalf of a larger collaboration, report:

Following the detection of GRB210726A by Swift (Bernardini et al. GCNC 30523), we triggered the 2.2m CAHA telescope (+ CAFOS) at the Calar Alto Observatory (Almeria, Spain). A series of i-band images were gathered starting on July 26, 20:23 UT (i.e. 1.07 h post trigger). On the co-added image (15 x 60s), no optical object is detected down to 21.9 mag at the X-ray afterglow position reported by Swift/XRT (Osborne et al. GCNC 30524).

We thank the staff at Calar Alto observatory for their excellent support.


GRB_name: GRB210725B
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30526
SUBJECT: GRB 210725B: Swift/UVOT Upper Limits
DATE:    21/07/27 00:38:22 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M. H. Siegel (PSU) and M. G. Bernardini (INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210725B
92 s after the BAT trigger (Bernardini et al., GCN Circ. 30508).
No optical afterglow consistent with the XRT position (Goad et al. GCN Circ. 30510)
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

u (fc)               92          341          246         >20.5
b                  347          439           91         >20.0
u                   92          341          246         >20.5
w2                3722         3905          180         >19.4

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.023 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210725A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30527
SUBJECT: GRB 210725A: Swift/UVOT Upper Limits
DATE:    21/07/27 00:40:13 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M. H. Siegel (PSU) and M. G. Bernardini (INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210725A
114 s after the BAT trigger (Bernardini et al., GCN Circ. 30501).
No optical afterglow consistent with the XRT position (Perri et al. GCN Circ. 30517)
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)         114          264          147         >20.7
u (fc)             273          523          246         >20.2
white              114         1545          392         >21.0
v                  603         1595          117         >19.1
b                  529         1519           97         >20.4
u                  273         1495          343         >20.4
w1                 653         1470           97         >19.2

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.047 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210723A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30528
SUBJECT: GRB 210723A: Swift/UVOT Upper Limits
DATE:    21/07/27 06:16:48 GMT
FROM:    Sam LaPorte at PSU  <sjl5346@psu.edu>

 GRB 210723A: Swift/UVOT Upper Limits

S. J. LaPorte (PSU) and Sbarrato (INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210723A
99 s after the BAT trigger (Sbarrato et al., GCN Circ. 30485).
No optical afterglow consistent with the XRT position
(Evans GCN Circ. 30486)
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            99          249          147         >20.6
u_FC               312          562          246         >19.2
white               99         1364          369         >20.6
v                  641         1241           78         >18.2
b                  567         1339           78         >19.3
u                  312         1315          304         >19.4
w1                 691         1290           58         >19.0
m2                 666         1266           78         >18.8
w2                 617         1217           78         >19.5

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.962 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210724A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30529
SUBJECT: GRB 210724A: Swift/UVOT Upper Limits
DATE:    21/07/27 06:17:13 GMT
FROM:    Sam LaPorte at PSU  <sjl5346@psu.edu>

 GRB 210724A: Swift/UVOT Upper Limits

S. J. LaPorte (PSU) and P. D'Avanzo (INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210724A
125 s after the BAT trigger (D'Avanzo et al., GCN Circ. 30497).
No optical afterglow consistent with the XRT position
(D'Avanzo et al. GCN Circ. 30497)
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           125          275          147         >20.8
u_FC               283          513          226         >20.1
white              125          275          147         >20.8
u                  283          513          227         >20.1

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.097 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210725A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30530
SUBJECT: GRB 210725A: AbAO optical upper limit
DATE:    21/07/27 06:54:14 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

N. Pankov (HSE, IKI),  R. Ya. Inasaridze (AbAO), A. Pozanenko (IKI), 
S. Belkin (IKI), V. R. Ayvazian (AbAO),  G. V. Kapanadze (AbAO), report 
on behalf of GRB IKI FuN:

We observed  the field of GRB 210725A (Bernardini et al. GCN 30501; 
Torii  et al. GCN 30507; Poolakkil et al. GCN 30519)  with AS-32 
telescope of Abastumani observatory (AbAO) in R-filter starting on July, 
25 (UT) 19:11:58. We do not detect any object in the enhanced XRT 
position (Perri et al. GCN 30517). The non detection is consistent with 
optical observations (Zheng  et al. GCN 30503; Niwano et al., GCN 30509; 
Siegel  et al. GCN 30527).

Preliminary photometry of the field  is following

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

2021-07-25 19:11:58   0.65481  R     36*60   n/d  n/d   20.8

The photometry is based on the nearby stars:
USNO-B1.0 R2
USNO_B10_id R2
0888-00234198 14.31
0888-00234167 15.25


GRB_name: GRB210727A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30531
SUBJECT: GRB 210727A: BALROG localization (Fermi Trigger 649072251 / GRB 210727410)
DATE:    21/07/27 11:44:42 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
649072251 at 09:50:46 on 27 July 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) = 184.2+/-6.6 deg
Decl.(2000.0) = -64.3+/-3.5 deg
We estimate an additional systematic error of 2 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210727410/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210727410/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210727410/json

                        


GRB_name: GRB210727A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30533
SUBJECT: GRB 210727A: AGILE/MCAL detection
DATE:    21/07/27 14:43:39 GMT
FROM:    Alessandro Ursi at INAF/IAPS  <alessandro.ursi@gmail.com>

A. Ursi (INAF/IAPS), F. Verrecchia (SSDC, and INAF/OAR), M. Pilia
(INAF/OA-Cagliari), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A.
Argan, M. Cardillo, C. Casentini, Y. Evangelista, G. Piano, A. Ursi
(INAF/IAPS), F. Lucarelli, C. Pittori (SSDC, and INAF/OAR), A. Bulgarelli,
V. Fioretti, F. Fuschino, N. Parmiggiani (INAF/OAS-Bologna), M. Marisaldi
(INAF/OAS-Bologna, and Bergen University), 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 Mini-CALorimeter (MCAL) detected the short GRB 210727A (Fermi
trigger no. 649072251) at T0 = 2021-07-27 09:50:47.40 +/- 0.01 s (UTC).

The event lasted about 1.5 s and released a total number of ~1300 counts in
the detector (in the 0.4-100 MeV energy range), above an average background
rate of 560 Hz. The MCAL light curve can be found at
http://www.agilescienceapp.it/notices/074097_GRB_MCAL_554464247.402495.png .

The time-integrated spectrum of the burst can be fitted in the energy range
0.4-20 MeV with a single power-law with ph.ind. = -1.59 -/+ 0.07, resulting
in a reduced chi-squared of 1.23 (62 d.o.f.) and a fluence of 9.6e-06
ergs/cm^2 (90% confidence level), in the same energy range.

The AGILE-MCAL detector is a CsI detector with a 4 pi FoV, sensitive in the
energy range 0.4-100 MeV. 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: GRB210726A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30534
SUBJECT: GRB 210726A: RATIR Optical Upper Limits and Candidate Host Galaxy 
DATE:    21/07/27 16:14:25 GMT
FROM:    Alan M Watson at UNAM  <alan@astro.unam.mx>

Alan M. Watson (UNAM), Eleonora Troja (GSFC), Nat Butler (ASU), Alexander
Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox
(STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Enrico Ramirez-Ruiz
(UCSC), JesÃºs GonzÃ¡lez (UNAM), Carlos RomÃ¡n-ZÃºÃ±iga (UNAM), Harvey Moseley
(GSFC), Rosa L. Becerra (UNAM), Simone Dichiara (UMD), and OcÃ©lotl LÃ³pez (UNAM)
report:

We observed the field of candidate short GRB 210726A (Bernardini et al., GCN
Circ., 30523) 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 2021/07 27.16 to 2021/07 27.22 UTC (8.24 to 9.65
hours after the BAT trigger), obtaining a total of 1.09 hours exposure in the r
and i bands.

For a source within the enhanced Swift-XRT error circle (Osborne et al., GCN
Circ., 30524), in comparison with the SDSS DR9 catalog, we obtain the following
upper limits (3-sigma):

  r > 23.0
  i > 22.7

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.

We note that the SDSS galaxy J125309.63+191127.2 is 3.1 arcsec from the enhanced
XRT position and just outside the error circle. In our observations, it has 
r = 22.2 +/- 0.2 and i = 22.2 +/- 0.2, in agreement with the cataloged values.
The cataloged photometric redshift is z = 0.35 +/- 0.15. The probability of a
chance alignment is approximately 3%. Given this low probability, we suggest
that this source might be the host galaxy.

Since this GRB appears to be potentially both short and low-redshift, we
encourage further observations.

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


GRB_name: GRB210726A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30535
SUBJECT: GRB 210726A: Likely a short burst
DATE:    21/07/27 16:59:24 GMT
FROM:    Aaron Tohuvavohu at U Toronto  <aaron.tohu@gmail.com>

GRB 210726A, detected by Swift BAT and XRT (GCN 30523) appears likely
to be a short burst, despite the real time duration estimate (~3s)
reported in the discovery circular using limited data products. The
T90 estimate derived from the full downlinked Swift/BAT event data is
less than 0.5 seconds.
Follow-up is encouraged.


GRB_name: GRB210726A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30536
SUBJECT: GRB 210726A: Swift-BAT refined analysis
DATE:    21/07/27 19:36:05 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

D. M. Palmer (LANL), S. D. Barthelmy (GSFC),
M. G. Bernardini (INAF-OAB), 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 210726A (trigger #1061687)
(Bernardini et al., GCN Circ. 30523).  The BAT ground-calculated position is
RA, Dec = 193.333, 19.211 deg which is
   RA(J2000)  =  12h 53m 19.9s
   Dec(J2000) = +19d 12' 38.9"
with an uncertainty of 2.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve shows a short spike that starts at ~T0,
peaks at ~T+0.2 s, and ends at ~T+0.4 s. Some tail emission from the
raw light curves was mentioned in the original circular (Bernardini et al.,
GCN Circ. 30523), and this potential weak tail can be seen in the 1-s
binned
light curve (15-350 keV) as well. However, image analyses from ~T+0.5 s
to ~T+2 s do not find any significant detections that are >~ 2 sigma.
Therefore, this signal is also consistent with noise fluctuation.
T90 (15-350 keV) is 0.39 +- 0.11 sec (estimated error including
systematics).

The time-averaged spectrum from T-0.00 to T+0.42 sec is best fit by
a simple power-law model.  The power law index of the time-averaged
spectrum is 1.54 +- 0.47.  The fluence in the 15-150 keV band is
4.5 +- 1.1 x 10^-8 erg/cm2. The 1-sec peak photon flux measured from
T-0.29 sec in the 15-150 keV band is 0.7 +- 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/1061687/BA/


GRB_name: GRB210726A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30537
SUBJECT: GRB 210726A: Swift-XRT refined Analysis
DATE:    21/07/27 19:57:58 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

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

We have analysed 5.9 ks of XRT data for GRB 210726A (Bernardini et al.
GCN Circ. 30523), from 79 s to 75.9 ks after the  BAT trigger. The data
are entirely in Photon Counting (PC) mode. The enhanced XRT position
for this burst was given by Osborne et al. (GCN Circ. 30524).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.49 (+0.22, -0.26).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.2 (+/-0.3). The
best-fitting absorption column is  3.3 (+1.3, -1.2) x 10^21 cm^-2, in
excess of the Galactic value of 1.7 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 3.3 x 10^-11 (5.7 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      3.3 (+1.3, -1.2) x 10^21 cm^-2
Galactic foreground: 1.7 x 10^20 cm^-2
Excess significance: 4.5 sigma
Photon index:      2.2 (+/-0.3)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01061687.

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


GRB_name: GRB210702A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30538
SUBJECT: GRB 210702A: MeerKAT radio detection
DATE:    21/07/27 22:40:49 GMT
FROM:    Tanmoy Laskar at U of Bath  <tanmoylaskar@gmail.com>

T. Laskar (University of Bath), S. Buchner (SARAO), S. Legodi (SARAO), K.
D. Alexander (Northwestern), E. Ayache (Bath), E. Berger (Harvard), S.
Bhandari (CSIRO), J. Bright (Northwestern), R. Chornock (UC Berkeley), D.
Coppejans (Northwestern), H. van Eerten (Bath), W. Fong (Northwestern), R.
Margutti (UC Berkeley), C.G. Mundell (Bath), P. Schady (Bath), and G.
Schroeder (Northwestern) report:

"We observed GRB 210702A (Lien et al. GCN 30351) with the MeerKAT radio
telescope array over two epochs beginning on 2021 July 11 12:16 UTC (8.7 d
after the burst) and 2021 July 23 18:16 UTC (21.0 d after the burst),
respectively. Preliminary analysis reveals a brightening radio counterpart
with 1.284 GHz flux density of 123 +/- 12 uJy at 21.0 d at position:

RA (J2000) = 11:14:18.76
Dec (J2000) = -36:44:49.5

with uncertainty ~ 0.4" in each coordinate, consistent with the X-ray
position (D'Elia et al., GCN 30358), optical position (Lien et al., GCN
30351; Kuin et al., GCN 30356), and mm-band position (Laskar & Perley, GCN
30423). Further observations are planned.

The MeerKAT telescope is operated by the South African Radio Astronomy
Observatory, which is a facility of the National Research Foundation, an
agency of the Department of Science and Innovation."


GRB_name: GRB210714A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30539
SUBJECT: GRB 210714A: Fermi GBM observation
DATE:    21/07/28 15:20:05 GMT
FROM:    Elisabetta Bissaldi at INFN,Bari  <elisabetta.bissaldi@ba.infn.it>

E. Bissaldi (Politecnico and INFN Bari)
reports on behalf of the Fermi GBM Team:
  

"At 07:56:33.25 UT on 14 July 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210714A (trigger 647942198 / 210714331),
which was also detected by Konus-Wind (Frederiks et al. 2021, GCN 30467).

The on-ground calculated location, using the GBM trigger data, is
RA = 313.67, DEC = -51.59
(J2000 degrees, equivalent to 20 h 54 m, -51 d 35'),
with a statistical uncertainty
of 1 degree (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which we have characterized as a core-plus-tail model, with 90% of
GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg
systematic error. [Connaughton et al. 2015, ApJS, 216, 32]).

The angle from the Fermi LAT boresight at the GBM trigger time is 109 degrees.

The GBM light curve consists of a bright, FRED-like pulse
with a duration (T90) of about 42 s (50-300 keV).
The time-averaged spectrum from T0 to T0+25 s is
best fit by a Band function with Epeak = 64 +/- 5 keV,
alpha = -0.68 +/- 0.09, and beta = -1.75 +/- 0.01.

The event fluence (10-1000 keV) in this time interval is
(4.67 +/- 0.15)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.9 s in the 10-1000 keV band
is 48.9 +/- 0.7 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: GRB210726A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30540
SUBJECT: Fermi GBM Sub-Threshold Detection of GRB 210726A
DATE:    21/07/28 15:21:41 GMT
FROM:    Peter Veres at UAH  <veresp@gmail.com>

P. Veres (UAH) reports on behalf of the Fermi-GBM Team:

"Swift-BAT detected GRB 210726A at 19:19:03 UT (GCN 30523). There was
no Fermi-GBM
onboard trigger around the event.

The GBM targeted search [1], the most sensitive, coherent search for
GRB-like signals was run from +/-30 s around the BAT trigger time.  A
transient source was identified whose most significant timescale according
to the search is 512 ms, and a location consistent with the Swift-BAT
event.  The GBM targeted search event was found with the highest
significance with a "soft" spectral template (Band function with Epeak = 70
keV, alpha = -1.9, beta = -3.7).

The GBM light curve consists of a single peak. The time-averaged spectrum
from T0+0.6 s to T0+1.4 s is best fit by a power law function with index
-2.03 +/- 0.3 (T0 is 2021-07-26 19:19:03 UT). A power law function with an
exponential high-energy cutoff fits equally well, but it is not
statistically preferred over the power law;  the fit measures the power law
index 0.23 +/- 1.67 and the cutoff energy, parameterized as Epeak, is 41
+/- 10 keV.

The event fluence (10-1000 keV) in this time interval for the power law
with the exponential cutoff is (6.4 +/- 1.7)E-08 erg/cm^2. Using the
photometric redshift z=0.35 reported by Watson et al. (GCN 30534), we
derive an isotropic equivalent energy in the 1-10,000 keV range of (2.1 +/-
0.5)E+49 erg.

This analysis is preliminary.

[1] Goldstein et al. 2019 arXiv:1903.12597
"


GRB_name: GRB210727A
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30541
SUBJECT: IPN triangulation of GRB 210727A (short)
DATE:    21/07/28 18:09:24 GMT
FROM:    Anna Ridnaia at Ioffe Institute  <ridnaia@mail.ioffe.ru>

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

K. Hurley, on behalf of the IPN,

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

S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu
on behalf of the Swift-BAT team, report:

The short-duration GRB 210727A
(BALROG localization: Biltzinger et al., GCN 30531;
AGILE-MCAL detection: Ursi et al., GCN 30533)
was detected by Fermi (GBM trigger 649072251), Konus-Wind,
INTEGRAL (SPI-ACS), Swift (BAT), AGILE (MCAL),
and CALET (CGBM) at about 35447 s UT (09:50:47).
The burst was outside the coded field of view of the BAT.

We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
 ---------------------------------------------
  RA(2000), deg                 Dec(2000), deg
 ---------------------------------------------
 Center:
  189.231 (12h 36m 55s) -59.926 (-59d 55' 35")
 Corners:
  194.539 (12h 58m 09s) -56.353 (-56d 21' 12")
  193.795 (12h 55m 11s) -56.308 (-56d 18' 30")
  182.624 (12h 10m 30s) -63.300 (-63d 17' 59")
  183.549 (12h 14m 12s) -63.394 (-63d 23' 37")
 ---------------------------------------------
The error box area is 3.28 sq. deg, and its maximum
dimension is 9.14 deg (the minimum one is 22 arcmin).
The Sun distance was 93 deg.

This box may be improved.

The IPN localization is consistent with, but reduces the area of, the
Fermi final position and the BALROG localization.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB210727_T35447/IPN

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


GRB_name: GRB210726A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30542
SUBJECT: GRB 210726A: 6 GHz VLA radio upper limit
DATE:    21/07/28 22:38:02 GMT
FROM:    Genevieve Schroeder at Northwestern University  <genevieveschroeder2023@u.northwestern.edu>

G. Schroeder, W. Fong, A. Rouco Escorial, (Northwestern), T. Laskar (U. of
Bath), E. Berger (Harvard) report:

"We observed the position of short GRB 210726A (Bernardini et al., GCN
30523; Veres et al., GCN 30540; Palmer et al., GCN 30536; Tohuvavohu et
al., GCN 30535) with the Karl G. Jansky Very Large Array (VLA) under
program 20B-057 (PI: Fong) beginning on 2021 July 27.81 UT (1.00 days
post-burst) at a mean frequency of 6 GHz.

Based on preliminary analysis, in 1 hour of observations we do not detect
any radio emission at or near the position of the XRT afterglow (Osborne et
al., GCN 30524) to a 3-sigma limit of 15 microJy. Additional, detailed
analysis is ongoing.

We thank the VLA staff for quickly approving and executing these
observations."


GRB_name: GRB210726A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30543
SUBJECT: GRB 210726A: Deep CAHA 2.2m limit
DATE:    21/07/29 00:01:25 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. Thoene, M. Blazek, J. F. Agui Fernandez (all 
HETH/IAA-CSIC), A. Gardini, and I. Hermelo (both CAHA) report:

We observed the XRT afterglow position (Osborne et al., GCN #30524) of 
GRB 210726A (Bernardini et al., GCN #30523), classified as a short GRB 
(Tohuvavohu, GCN #30535; Palmer et al., GCN #30536; Veres, GCN #30540) 
with CAFOS mounted at the 2.2m Calar Alto telescope (Almeria, Spain), 
under good conditions but at high airmass, starting July 26, 20:52:13 
UT, 1.553 h after the GRB. We obtained 15 x 180 s images in r'.

Within the XRT error circle, we do not detect any source down to r' > 
24.2 mag (AB magnitude) at 0.081518 d (1.956 h) after the burst, in 
agreement with but deeper than limits presented by Hu et al., GCN 
#30525; Watson et al., GCN #30534.

Watson et al. suggest an object about 3" away as a possible host-galaxy 
candidate. We clearly detect this object and measure r' = 22.26 +/- 0.06 
mag. This value is in agreement with detections from the PanSTARRS and 
SDSS surveys, and therefore there is no evidence of excess emission that 
could be an afterglow superposed on the host galaxy.


GRB_name: GRB210727A
Detection_method: CALET
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30544
SUBJECT: GRB 210727A: CALET Gamma-Ray Burst Monitor detection
DATE:    21/07/29 10:11:54 GMT
FROM:    Valentin Pal'shin at AGU  <val@phys.aoyama.ac.jp>

Y. Akaike (Waseda U),
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, 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 210727A (BALROG localization: Biltzinger et al.,
GCN Circ. 30531; AGILE/MCAL detection: Ursi et al., GCN Circ. 30533;
IPN triangulation: Ridnaia et al., GCN Circ. 30541;
https://gcn.gsfc.nasa.gov/other/210727A.gcn3) triggered the CALET Gamma-ray
Burst Monitor (CGBM) at 09:50:46.605 UTC on 27 July 2021.
The burst signal was seen by all CGBM detectors.

The burst light curve shows a multi-peaked structure which starts at
T-0.38 sec and ends at T+0.64 sec. The T90 and T50 durations measured by
the SGM data are 0.96 +- 0.14 sec and 0.51 +- 0.09 sec (40-1000 keV),
respectively.

The ground processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1311414395/

The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at the Waseda University.


GRB_name: GRB210726A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30545
SUBJECT: GRB 210726A: OSIRIS/GTC observations
DATE:    21/07/29 12:54:52 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. Thoene, M. Blazek, J. F. Agui Fernandez (all 
HETH/IAA-CSIC), J. P. U. Fynbo (DAWN/NBI), L. Izzo (DARK/NBI), N. R. 
Tanvir (U. Leicester), and G. Gomez Velarde (GRANTECAN) report:

We observed the XRT afterglow position (Osborne et al., GCN #30524) of 
GRB 210726A (Bernardini et al., GCN #30523), classified as a short GRB 
(Tohuvavohu, GCN #30535; Palmer et al., GCN #30536; Veres, GCN #30540) 
with OSIRIS mounted on the 10.4m Gran Telescopio Canarias (Observatorio 
AstrofÃ­isco Roque de Los Muchachos, La Palma, Canary Islands, Spain), 
under mediocre conditions and at high airmass, starting July 26, 
21:21:31 UT, 2.041 h after the GRB. We obtained a sequence of 30, 30, 
60, 30 s images in r' for a total integration time of 150 s.

Within the XRT error circle, we do not detect any source down to r' > 
24.4 mag (AB magnitude), measured against a nearby PanSTARRS fiel star, 
at 0.088533 d (2.125 h) after the burst, in agreement with Kann et al., 
GCN #30543.

The possible host galaxy (Watson et al., GCN #30534, Kann et al., GCN 
#30543) is found at r' = 22.04 +/- 0.05 mag, again in agreement with 
detections from the PanSTARRS and SDSS surveys.


GRB_name: GRB210725B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30546
SUBJECT: Fermi GBM Sub-Threshold Detection of GRB 210725B
DATE:    21/07/29 15:10:40 GMT
FROM:    Cori Fletcher at USRA  <cfletcher@usra.edu>

C. Fletcher (USRA) reports on behalf of the Fermi-GBM Team:

Swift-BAT detected GRB 210725B at 12:00:48 UT (GCN 30508). There was no
Fermi-GBM onboard trigger around the event.

An automated, blind search for short gamma-ray bursts below the onboard
triggering threshold in Fermi-GBM identified a transient source at this time.

The GBM targeted search [1], the most sensitive, coherent search for
GRB-like signals identified a transient most significantly on the 8.192 s
timescale, with a false alarm rate of 2.6e-05 Hz and a location consistent with
the Swift-BAT event, using the standard search protocol with a S/N of 9.
The GBM targeted search event was found with the highest
significance with a "normal" spectrum (Band function with
Epeak = 230 keV, alpha = -1.0, beta = -2.3) for a GRB.

[1] Goldstein et al. 2019 arXiv:1903.12597


GRB_name: GRB210724A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30547
SUBJECT: GRB 210724A: Corrected Swift-XRT enhanced position
DATE:    21/07/29 15:25:48 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans (U. Leicester) and P. D'Avanzo (INAF-OAB) report on behalf of 
the Swift-XRT team.

The XRT position of GRB 210724A reported in GCN Circ. 30515 was 11" from 
the position of the optical candidate found by de Ugarte Postigo et al. 
(GCN Circ. 30511). Unusually, this position underwent significant 
variation during the normal revisions after each data downlink. 
Investigation has revealed a rare local minimum issue during the first 
XRT image, which has now been fixed.

The best XRT position is RA, Dec = 227.41461, -6.29070 which is 
equivalent to:

RA (J2000): 15h 09m 39.51s
Dec(J2000): -06d 17' 26.5"

with an uncertainty of 3.0 arcsec (radius, 90% confidence). This 
position is 1.1" from the optical position of de Ugarte Postigo et al.

We apologise for the confusion caused by this rare glitch, which 
coincided with the author's vacation (Murphy et al).

As ever, the most recent version of the position can be found online at:
https://www.swift.ac.uk/xrt_positions/01061482/


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


GRB_name: GRB210730A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30548
SUBJECT: GRB 210730A: Swift detection of a burst near M82
DATE:    21/07/30 05:23:03 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

E. Sonbas (Adiyaman Univ.), S. D. Barthelmy (GSFC),
A. D'Ai (INAF-IASFPA), D. M. Palmer (LANL), T. Sakamoto (AGU),
B. Sbarufatti (PSU) and M. H. Siegel (PSU) report on behalf of the
Neil Gehrels Swift Observatory Team:

At 04:57:29 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210730A (trigger=1062150).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 149.592, +69.705 which is 
   RA(J2000) = 09h 58m 22s
   Dec(J2000) = +69d 42' 19"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  Although the BAT lightcurve is not immediately
available due to telemetry limitations, the trigger information indicates
a very bright peak (68 sigma in rates) of at least 1 second duration. 

The XRT began observing the field at 04:58:50.8 UT, 81.6 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 149.59149, 69.69227 which
is equivalent to:
   RA(J2000)  = 09h 58m 21.96s
   Dec(J2000) = +69d 41' 32.2"
with an uncertainty of 8.2 arcseconds (radius, 90% containment). This
location is 45 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 2.5 s image was 6.73e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 113 seconds with the White filter
starting 90 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image processing
FAILED because of no aspect solution. Data from the list of sources generated
on-board are not available at this time. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.096. 

We note that this location is close to the nearby galaxy M82, although
well outside the main disk.  For this reason, the initial GCN Notice
misreported it as a Galactic transient. 

Burst Advocate for this burst is E. Sonbas (edasonbas AT yahoo.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: GRB210727A
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30549
SUBJECT: GRB 210727A: AstroSat CZTI detection
DATE:    21/07/30 06:21:59 GMT
FROM:    Gaurav Waratkar at IIT,Bombay  <gauravwaratkar@iitb.ac.in>

V. Prasad (IUCAA), P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute
(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 short GRB 210727A, which
was also detected by Fermi-GBM (Trigger no. 649072251), AGILE/MCAL (Ursi
et al., GCN 30533), CALET (Akaike et al., GCN 30544), with IPN
localization (Ridnaia et al., GCN 30541) and BALROG localization
(Biltzinger et al., GCN 30531). 

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
2021-07-27 09:50:46.45 UT. The measured peak count rate associated with
the burst is 890 (+197, -153) cts/s above the background in the combined
data of four quadrants, with a total of 489 (+74, -67) cts. The local
mean background count rate was 482 (+11, -15) cts/s. Using cumulative
rates, we measure a T90 of 0.9 (+0.3, -0.1) s.

It was also detected in the CsI anticoincidence (Veto) detector in the
100-500 keV energy range.  

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: GRB210730A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30550
SUBJECT: GRB 210730A: Enhanced Swift-XRT position
DATE:    21/07/30 07:16:48 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 40 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 210730A, 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 = 149.59012, +69.68936 which is equivalent
to:

RA (J2000): 09h 58m 21.63s
Dec (J2000): +69d 41' 21.7"

with an uncertainty of 4.5 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: GRB210724A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30551
SUBJECT: GRB 210724A: Early CAHA 2.2m limit
DATE:    21/07/30 12:37:10 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. Thoene, M. Blazek, J. F. Agui Fernandez (all 
HETH/IAA-CSIC), A. Gardini, and I. Hermelo (both CAHA) report:

We observed the in-flight XRT afterglow position (revised in Evans et 
al., GCN #30547) of GRB 210724A (D'Avanzo et al., GCN #30497) with CAFOS 
mounted at the 2.2m Calar Alto telescope (Almeria, Spain), under very 
adverse conditions (high airmass, strong Calima, clouds, bad seeing, 
strong moonlight - the works). We obtained 10 x 180 s images in r', 
starting on July 24, 21:07:08 UT (0.8831 h after the burst).

At the position of the GTC afterglow candidate (de Ugarte Postigo et 
al., GCN #30511), we detect no source down to r' > 22.0 mag (AB 
magnitude) against PanSTARRS comparison stars, at midtime 0.0482 d 
(1.1569 h) after the burst. This is of similar depth as the detection by 
de Ugarte Postigo et al., GCN #30511, perhaps indicating a slowly rising 
afterglow, or at least one that is not steeply decaying.


GRB_name: GRB210730A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30552
SUBJECT: GRB 210730A: Swift/UVOT Upper Limits
DATE:    21/07/30 13:13:09 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

N. P. M. Kuin (UCL-MSSL) and E. Sonbas (Adiyaman Univ.)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210730A
90 s after the BAT trigger (Sonbas et al., GCN Circ. 30548).
No optical afterglow consistent with the XRT position
(Beardmore et al. GCN Circ. 30550)
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            90          204          112         >17.0
white               90         4145          308         >16.7
v                 4355         4555          197         >15.5
b                 3740         3940          197         >16.4
u                 3535         5146          370         >16.5
w1                4765         4965          197         >18.0
m2                4560         4760          197         >19.7
w2                4151         4351          197         >18.6

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.097 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210730A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30553
SUBJECT: GRB 210730A: Swift-XRT refined Analysis
DATE:    21/07/30 16:33:52 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU),
P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester), A. Melandri (INAF-OAB), T. Sbarrato (INAF-OAB), P. D'Avanzo
(INAF-OAB) and E. Sonbas report on behalf of the Swift-XRT team:

We have analysed 9.1 ks of XRT data for GRB 210730A (Sonbas et al. GCN
Circ. 30548), from 87 s to 33.8 ks after the  BAT trigger. The data
comprise 71 s in Windowed Timing (WT) mode with the remainder in Photon
Counting (PC) mode. The enhanced XRT position for this burst was given
by Beardmore et al. (GCN Circ. 30550).

The light curve can be modelled with an initial power-law decay with an
index of alpha=6.1 (+1.6, -2.1), followed by a break at T+107 s to an
alpha of 1.18 (+/-0.04).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.4 (+/-0.3). The
best-fitting absorption column is  6.7 (+2.0, -1.7) x 10^21 cm^-2, in
excess of the Galactic value of 6.3 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 3.5 x 10^-11 (8.2 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      6.7 (+2.0, -1.7) x 10^21 cm^-2
Galactic foreground: 6.3 x 10^20 cm^-2
Excess significance: 5.9 sigma
Photon index:      2.4 (+/-0.3)

If the light curve continues to decay with a power-law decay index of
1.18, the count rate at T+24 hours will be 3.1 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x
10^-13 (2.5 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/01062150.

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


GRB_name: GRB210730A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30554
SUBJECT: GRB 210730A: Swift-BAT refined analysis
DATE:    21/07/30 17:05:35 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.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), E. Sonbas (Adiyaman Univ.),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-240 to T+200 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 210730A (trigger #1062150)
(Sonbas et al., GCN Circ. 30548).  The BAT ground-calculated position is
RA, Dec = 149.570, 69.703 deg which is
   RA(J2000)  =  09h 58m 16.8s
   Dec(J2000) = +69d 42' 12.4"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 55%.

The mask-weighted light curve shows a single-peaked structure that
starts at ~T-0.5, peaks at ~T+0.5, and ends at ~T+5. T90 (15-350 keV)
is 3.86 +- 0.66 sec (estimated error including systematics).

The time-averaged spectrum from T-0.32 to T+5.01 sec is best fit by
a simple power-law model.  The power law index of the time-averaged
spectrum is 1.41 +- 0.11.  The fluence in the 15-150 keV band
is 1.3 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured
from T+0.17 sec in the 15-150 keV band is 7.1 +- 0.5 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/1062150/BA/


GRB_name: GRB210730A
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30555
SUBJECT: GRB 210730A: AstroSat CZTI detection
DATE:    21/07/30 17:16:49 GMT
FROM:    Gaurav Waratkar at IIT,Bombay  <gauravwaratkar@iitb.ac.in>

V. Prasad (IUCAA), P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute
(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 the detection of a long GRB 210730A,
which was also detected by Swift-BAT (Sonbas et al., GCN 30548, Sakamoto
et al., GCN 30554) and Swift-XRT (Beardmore et al., GCN 30550).

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
2021-07-30 04:57:28.55 UT. The measured peak count rate associated with
the burst is 502 (+181, -71) cts/s above the background in the combined
data of four quadrants, with a total of 621 (+161, -206) cts. The local
mean background count rate was 508 (+12, -11) cts/s. Using cumulative
rates, we measure a T90 of 3.3 (+1.1, -1.9) s.

It was also clearly detected in the CsI anticoincidence (Veto) detector
in the 100-500 keV energy range. 

CZTI GRB detections are reported regularly on the payload site at
http://astrosat.iucaa.in/czti/?q=grb [1]. 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. 

Links:
------
[1] http://astrosat.iucaa.in/czti/?q=grb


GRB_name: GRB210730A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30557
SUBJECT: GRB 210730A: Fermi GBM observation
DATE:    21/07/30 21:05:04 GMT
FROM:    Joshua Wood at MSFC/Fermi-GBM  <joshua.r.wood@nasa.gov>

J. Wood (NASA/MSFC)
reports on behalf of the Fermi GBM Team:

"At 04:57:29.03 UT on 30 July 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210730A (trigger 649313854 / 210730207)
which was also detected by the Swift/BAT and Swift/XRT (E. Sonbas et al. 2021, GCN 30548).

The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 32 degrees.

The GBM light curve consists of a single peak
with a duration (T90) of about 5 s (50-300 keV).
The time-averaged spectrum from T0 to T0+6 s is
well fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.68 +/- 0.07 and
the cutoff energy, parameterized as Epeak, is 170 +/- 11 keV

The event fluence (10-1000 keV) in this time interval is
(2.9 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0.3 s in the 10-1000 keV band
is 10.5 +/- 0.3 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: GRB210726A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30558
SUBJECT: GRB 210726A: Chandra detection of the X-ray afterglow 
DATE:    21/07/30 23:26:02 GMT
FROM:    Alicia Rouco Escorial at CIERA  <alicia.rouco.escorial@northwestern.edu>

A. Rouco Escorial, W. Fong, K. Paterson (Northwestern University), R. Margutti (UC Berkeley) and E. Berger (Harvard University) report:



â€œWe initiated observations with the Chandra X-ray Observatory of the short-duration GRB 210726A (Bernardini et al., GCN 30523; Tohuvavohu, GCN 30535; Palmer, GCN 30536) starting on 2021 July 29 16:04:38 UT, with a median observation time of ~3 days post-trigger. We obtained one ACIS-S observation under the Proposal 22400461 (ObsID 23445; PI: Fong), with an effective exposure time of ~24.6 ks.

We obtain a ~7sigma detection of GRB 210726A with a total net source counts of 76+/-10 (0.5-7 keV). The Chandra position of the short GRB is fully consistent with the enhanced Swift-XRT position (90% confidence; XRT GRB catalogue, Evans et al., 2009). The Chandra position is:

RA(J2000)= 12h53m09.7s
Dec(J2000)=19d11m24.6s

with a total positional uncertainty of 0.81 arcsec (largely dominated by Chandra's absolute astrometric uncertainty).

Based on our MCMC modeling, the XRT and Chandra afterglow flux, starting at ~120.89 s post-burst, can be modeled with a broken power-law decline characterized by a second segment with a decay index (F~t^alpha) of alpha2=-0.62 (-0.05,+0.04) starting at ~418 s post-burst. In particular, the Chandra detection roughly follows the latest decline rate based on XRT data alone..

Further Chandra observations are planned. We thank the Chandra Director, Pat Slane, and staff for the rapid planning and scheduling of these observations.â€


GRB_name: GRB210730A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30560
SUBJECT: GRB 210730A: TNG optical observations
DATE:    21/07/31 02:05:32 GMT
FROM:    Paolo D'Avanzo at INAF-OAB  <pda.davanzo@gmail.com>

P. D'Avanzo (INAF-OAB), V. D'Elia (ASI-SSDC), M. Della Valle (INAF-OACN) A. Melandri (INAF-OAB), A. Rossi (INAF-OAS), 
G. Tagliaferri (INAF-OOAB), A. Harutyunyan, D. Carosati (INAF-TNG) on behalf of the CIBO collaboration report:

We observed the field of GRB 210730A (Sonbas et al., GCN Circ. 30548; Prasad et al., GCN Circ. 30555; Wood et al., GCN Circ. 30577) 
with the Italian 3.6m TNG telescope equipped with the optical camera DOLORES. A series of images were obtained with the r-sdss filter 
on 2021-07-30 from 21:41:57 UT to 22:08:38 UT (i.e. about 17 hours after the burst).  

At the edge of the XRT error circle (https://www.swift.ac.uk/xrt_positions/01062150/) we detect a faint optical source at the following 
position (J2000): 
RA: 09:58:21.96
Dec: +69:41:23.6
(+/- 1.0"). 


With preliminary photometry, carried out using a small aperture to minimise contamination from a nearby bright star, we derive the following 
magnitude:
r = 22.7  +/- 0.2 

(AB; calibrated against the SDSS catalogue). 
In our co-added image we reach a limiting magnitude of r ~ 23.5 (AB, 3sigma c.l.). 

We note that the same source is visible in archival Pan-STARRS images. Using a common set of reference stars and carrying out differential 
photometry on TNG and Pan-STARRS images we find no evidence for a change in magnitude of this source. 

Therefore, this source is likely not related to GRB 210730A. Alternatively, it can be the GRB host galaxy.


GRB_name: GRB210730A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30562
SUBJECT: Swift GRB 210730A: Global MASTER-Net observations report 
DATE:    21/07/31 05:00:27 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-Tavrida robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the Swift GRB 210730A ( E. Sonbas et al., GCN 30548) errorbox  47961 sec after notice time and 47903 sec after trigger time at 2021-07-30 18:17:14 UT, with upper limit up to  19.2 mag. Observations started at twilight.  The observations began at zenith distance = 54 deg. The sun  altitude  is -11.0 deg. 

MASTER-IAC robotic telescope  located in Spain (IAC Teide Observatory) was pointed to the Swift GRB 210730A errorbox  64883 sec after notice time and 64826 sec after trigger time at 2021-07-30 22:59:17 UT, with upper limit up to  17.7 mag. The observations began at zenith distance = 76 deg. The sun  altitude  is -34.0 deg. 

MASTER-Kislovodsk robotic telescope  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 210730A errorbox  71489 sec after notice time and 71432 sec after trigger time at 2021-07-31 00:49:22 UT, with upper limit up to  16.5 mag. Observations started at twilight.  The observations began at zenith distance = 65 deg. The sun  altitude  is -11.7 deg. 

The galactic latitude b = 41 deg., longitude l = 141 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1675497

We obtain a following upper limits.  

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

   47934 |      MASTER-Tavrida |   C |    60 | 17.0 |        
   48488 |      MASTER-Tavrida |   C |    60 | 17.9 |        
   48962 |      MASTER-Tavrida |   C |    60 | 18.4 |        
   49437 |      MASTER-Tavrida |   C |    60 | 18.8 |        
   49912 |      MASTER-Tavrida |   C |    60 | 18.7 |        
   50386 |      MASTER-Tavrida |   C |    60 | 19.1 |        
   50684 |      MASTER-Tavrida |   C |   180 | 18.9 |        
   51671 |      MASTER-Tavrida |   C |   180 | 19.2 |        
   64916 |          MASTER-IAC |   C |   180 | 17.5 |        
   64916 |          MASTER-IAC |   C |   180 | 17.3 |        
   65096 |          MASTER-IAC |   C |   540 | 17.7 |  Coadd 
   65131 |          MASTER-IAC |   C |   180 | 17.2 |        
   65131 |          MASTER-IAC |   C |   180 | 16.8 |        
   65311 |          MASTER-IAC |   C |   540 | 17.5 |  Coadd 
   65341 |          MASTER-IAC |   C |   180 | 17.2 |        
   65341 |          MASTER-IAC |   C |   180 | 17.0 |        
   65551 |          MASTER-IAC |   C |   180 | 17.1 |        
   65551 |          MASTER-IAC |   C |   180 | 16.8 |        
   65760 |          MASTER-IAC |   C |   180 | 17.0 |        
   65760 |          MASTER-IAC |   C |   180 | 17.0 |        
   65970 |          MASTER-IAC |   C |   180 | 17.2 |        
   65970 |          MASTER-IAC |   C |   180 | 16.7 |        
   66179 |          MASTER-IAC |   C |   180 | 17.0 |        
   66179 |          MASTER-IAC |   C |   180 | 16.9 |        
   66394 |          MASTER-IAC |   C |   180 | 17.1 |        
   66394 |          MASTER-IAC |   C |   180 | 16.8 |        
   66604 |          MASTER-IAC |   C |   180 | 17.0 |        
   66604 |          MASTER-IAC |   C |   180 | 16.8 |        
   66815 |          MASTER-IAC |   C |   180 | 17.1 |        
   66815 |          MASTER-IAC |   C |   180 | 16.6 |        
   67023 |          MASTER-IAC |   C |   180 | 17.0 |        
   67023 |          MASTER-IAC |   C |   180 | 16.7 |        
   67238 |          MASTER-IAC |   C |   180 | 17.0 |        
   67238 |          MASTER-IAC |   C |   180 | 16.7 |        
   67565 |          MASTER-IAC |   C |    60 | 16.7 |        
   67834 |          MASTER-IAC |   C |    60 | 16.7 |        
   67834 |          MASTER-IAC |   C |    60 | 16.2 |        
   67923 |          MASTER-IAC |   C |    60 | 16.0 |        
   68440 |          MASTER-IAC |   C |   180 | 16.9 |        
   68440 |          MASTER-IAC |   C |   180 | 16.6 |        
   68770 |          MASTER-IAC |   C |    60 | 16.4 |        
   69041 |          MASTER-IAC |   C |    60 | 16.5 |        
   69041 |          MASTER-IAC |   C |    60 | 16.0 |        
   69130 |          MASTER-IAC |   C |    60 | 15.7 |        
   69636 |          MASTER-IAC |   C |   180 | 16.6 |        
   69636 |          MASTER-IAC |   C |   180 | 16.3 |        
   69964 |          MASTER-IAC |   C |    60 | 16.2 |        
   70235 |          MASTER-IAC |   C |    60 | 16.4 |        
   70235 |          MASTER-IAC |   C |    60 | 15.8 |        
   70323 |          MASTER-IAC |   C |    60 | 15.5 |        
   70835 |          MASTER-IAC |   C |   180 | 16.4 |        
   70835 |          MASTER-IAC |   C |   180 | 15.9 |        
   71522 |   MASTER-Kislovodsk |   C |   180 | 16.5 |        
   71722 |   MASTER-Kislovodsk |   C |   180 | 16.1 |        
   72000 |          MASTER-IAC |   C |   180 | 16.1 |        
   72000 |          MASTER-IAC |   C |   180 | 16.0 |        
   73190 |          MASTER-IAC |   C |   180 | 15.8 |        
   73190 |          MASTER-IAC |   C |   180 | 15.9 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210730A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30563
SUBJECT: GRB 210730A: BOOTES-5/JGT and 2.2m CAHA telescopes optical limit
DATE:    21/07/31 12:31:26 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

Y.-D. Hu, T.-R. Sun, I. Carrasco, E. Fernandez-Garcia, A. J. Castro-Tirado and M. D. Caballero-Garcia (IAA-CSIC), D. Hiriart and W. H. Lee (UNAM), I. H. Park (SKKU), S. Gongora and I. Vico (CAHA) on behalf of a larger collaboration, report:

The 60cm BOOTES-5/JGT robotic telescope at Observatorio Astronomico Nacional in San Pedro Martir (Mexico) automatically followed up GRB 210730A (Sonbas et al., GCNC 30548) starting at 05:56:36 UT (~1 hr after trigger). Within the Swift/XRT error position (Beardmore et al., GCNC 30550), no new optical afterglow is found down to 20.9 mag in the co-added images (clear filter, 20x60 s).

We also triggered 2.2m CAHA telescope (+ CAFOS) at the Calar Alto Observatory (Almeria, Spain) to follow up this event. A series of gri-bands images were gathered starting on July 30, 20:25 UT (i.e. 15.5 h post trigger). On the co-added image (r-band, 15 x 60s), no new optical object is detected down to 23.0 mag at the X-ray afterglow position reported by Swift/XRT (Beardmore et al., GCNC 30550), consistent with the TNG non-detection (D'Avanzo et al., GCNC 30560).

We thank the staff at San Pedro Martir and Calar Alto Observtories for their excellent support.


GRB_name: GRB210730A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30564
SUBJECT: GRB 210730A: Campo Imperatore optical observations
DATE:    21/07/31 14:13:28 GMT
FROM:    Fiore De Luise at INAF-Osservatorio Astro. d'Abruzzo  <fiore.deluise@inaf.it>

F. De Luise, F. Onori (INAF-OAAb), R. Carini, S Piranomonte (INAF-OAR), A.
Melandri (INAF-OAB), M. Canzari, M. Dolci, G. Valentini, A. Di Cianno, A.
Valentini, N. Napoleone, P. Tedesco (INAF-OAAb), E. Brocato (INAF-OAAb and
OAR) on behalf of the GRAWITA collaboration report:

On 2021-07-30 we observed the field of GRB210730A (Sonbas et al., GCN Circ.
30548; Prasad et al., GCN Circ. 30555; Wood et al., GCN Circ. 30577) with
the 0.9m Schmidt Telescope of the INAF - Astronomical Observatory of
Abruzzo located at 2150 meters a.s.l. at Campo Imperatore (Italy) and
equipped with a 4096x4096 CCD, covering a field of view of 1.15Ã—1.15 square
degrees.

A series of optical images of the field have been obtained with the r-Sloan
and z-Sloan filters on 2021-07-30. The observation started at 19:50:29 UT
(about 15 hr after the burst) for a total exposure time of 26x180s in r
band and 15x180s in z band, respectively.
A preliminary analysis does not show any optical counterpart candidate
within the XRT error circle (https://www.swift.ac.uk/xrt_positions/01062150/
).


GRB_name: GRB210731A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30568
SUBJECT: GRB 210731A: Swift detection of a burst
DATE:    21/07/31 22:34:42 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

E. Troja (NASA/GSFC/UMCP), E. Ambrosi (INAF-IASFPA),
V. D'Elia (SSDC & INAF-OAR), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), B. Sbarufatti (PSU) and
A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 22:21:08 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210731A (trigger=1062336).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 300.314, -28.042 which is 
   RA(J2000) = 20h 01m 15s
   Dec(J2000) = -28d 02' 30"
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 ~0 sec after the trigger. 

The XRT began observing the field at 22:24:29.4 UT, 200.9 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 300.3036, -28.0595 which is equivalent to:
   RA(J2000)  = 20h 01m 12.86s
   Dec(J2000) = -28d 03' 34.2"
with an uncertainty of 5.8 arcseconds (radius, 90% containment). No
event data are yet available to determine the column density using
X-ray spectroscopy. 

The initial flux in the 2.5 s image was 7.96e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of  63 seconds with the White filter
starting 210 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
0.092. 

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: GRB210731A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30569
SUBJECT: GRB210731A: Enhanced Swift-XRT position
DATE:    21/08/01 09:24:41 GMT
FROM:    Antonino D'Ai at IASF-PA  <antonino.dai@inaf.it>

Antonino D'Ai (INAF-iASFPA), P.A. Evans and M.R. Goad (U. Leicester) report
on behalf of the Swift-XRT team:

Using 963 s of XRT Photon Counting mode data and 4 UVOT
images, 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 =
300.30500, -28.06105 which is equivalent to:

RA (J2000):  20 01 13.20
Dec (J2000): -28 03 39.8

with an uncertainty of 2.6 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 is an official product of the Swift-XRT team.


GRB_name: GRB210731A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30570
SUBJECT: GRB 210731A: MeerLICHT optical afterglow detection
DATE:    21/08/01 09:28:36 GMT
FROM:    Simon de Wet at UCT  <dwtsim002@myuct.ac.za>

S. de Wet (UCT), A.J. Levan (Radboud), P.J. Groot (Radboud/UCT/SAAO)
P.M. Vreeswijk (Radboud) report on behalf of the MeerLICHT consortium:

Following the detection of GRB210731A by Swift and its X-ray
counterpart (Troja et al., GCN30568), the 0.6m MeerLICHT telescope,
located at Sutherland, South Africa obtained a repeating series of
60s images in the q,u,q,g,q,r,q,i,q,z bands. Observations began at
2021-07-31, 22:25:54 UT, 5 minutes after the Swift detection, and
3 minutes after the distribution of the BAT alert, and continued
until 2021-08-01, 02:40:21 UT.

We find a new transient candidate in our first q-band exposure (318
seconds post-trigger) with magnitude q = 19.50 +/- 0.09 at coordinates:

RA (J2000) = 20:01:13.19 (300.30494d)
Dec (J2000) = -28:03:40.10 (-28.06114d)

calibrated against Gaia DR2. This position is 0.3" from the updated
XRT position, and which we regard as the optical afterglow to
GRB210731A. We note that no credible afterglow candidate was reported
by UVOT at ~210s post burst (Troja et al., GCN30568).

We detect the afterglow in further observations in the q,g,r and i
bands but not in u and z. Our q-band light curve shows a complex
shape with a steep rise and drop of ~0.7 mag within the first 2000s,
then a gradual rise of 0.7 mag for a further 3000s and a plateau
until ~10000s post-trigger.  The final q-band magnitude of the
source was q=18.95 +/- 0.07 at 2021-08-01, 01:06:47 UT. Our first
g,r and i source detections and u and z non-detections are, at:

g = 18.93 +/- 0.06 at 22:31:29 UT
r = 18.63 +/- 0.06 at 22:34:59 UT
i = 18.34 +/- 0.09 at 22:38:33 UT
u > 19.40 at 22:28:06 UT
z > 18.57 at 22:41:58 UT

Reference images of the field show no underlying host galaxy down
to the 5-sigma limiting magnitude, at the position of the afterglow,
at: q > 20.95. There is also no source identified at this location
in archival PanSTARRS images of the field.

MeerLICHT is built and run by a consortium consisting of Radboud
University, University of Cape Town, the South African Astronomical
Observatory, the University of Oxford, the University of Manchester
and the University of Amsterdam.


GRB_name: GRB210731A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30572
SUBJECT: GRB 210731A: Swift/UVOT Detection of an optical afterglow
DATE:    21/08/01 14:44:28 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

N. P. M. Kuin (UCL-MSSL) 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 210731A
210 s after the BAT trigger (Troja et al., GCN Circ. 30568).
An optical afterglow consistent with the XRT position (D'Ai et al.
GCN Circ. 30569) and discovered by Meerlicht (de Wet ert al, GCN Circ.
30570) is also detected in the initial UVOT exposures. Interestingly, the
initial rise to peak is slow.

Preliminary 3-sigma magnitudes using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures
are:

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

white              210          273           62         20.2  +/- 0.38
b                17547        18204          587         19.02 +/- 0.08
u                29863        30504          624         18.66 +/- 0.09
v                11787        12145          348         18.60 +/- 0.17
uvw1             28956        29857          886         19.33 +/- 0.14
uvw2             34767        35667          886         20.41 +/- 0.27
uvm2             23308        23846          530         19.40 +/- 0.21

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.092 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210731A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30573
SUBJECT: GRB 210731A: Fermi GBM Observation
DATE:    21/08/01 15:26:20 GMT
FROM:    Oliver J Roberts at USRA/NASA  <oliver.roberts@nasa.gov>

S. Lesage (UAH) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 22:21:07 UT on 31 July 2021, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 210731A (trigger 649462872/210731931)
which was also detected by Swift BAT (E. Troja et al. 2021, GCN 30568).
The Fermi GBM on-ground location is consistent with the Swift BAT position.

The angle from the Fermi LAT boresight is 102 degrees.

The GBM light curve consists of a single emission episode with a duration (T90)
of about 26 s (10-1000 keV). The time-averaged spectrum
from T0+0.003 to T0+19.968 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.1 +/- 0.1 and the cutoff energy,
parameterized as Epeak, is 175 +/- 11 keV.

The event fluence (10-1000 keV) in this time interval is
(4.9 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+10.3 s in the 10-1000 keV band is 2.9 +/- 0.3 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: GRB210731A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30574
SUBJECT: GRB 210731A: GROND observations
DATE:    21/08/01 16:26:36 GMT
FROM:    Ana Nicuesa at TLS Tautenburg  <ana@tls-tautenburg.de>

A. Nicuesa Guelbenzu, S. Klose, S. Schmidl (all TLS Tautenburg)
and A. Rau (MPE Garching) report:

We observed the field of GRB 210731A (Swift trigger 1062336; Troja et
al., GCN 30568) simultaneously in g'r'i'z'JHK with GROND mounted at
the 2.2m MPG telescope at ESO La Silla Observatory (Chile).

Observations started on 01-AUG-2021 at 02:33 UT, about 4.2 hours after
the GRB trigger. They were performed at an average seeing of 1.0
arcsec and at an average airmass of 1.1.

At a meantime of 2:46 UT, for the GRB afterglow (de Wet et al,
GCN 30570; Kuin et al., GCN 30572) we measure the following AB
magnitudes:

g' = 18.71 +/- 0.01 mag,
r' = 18.44 +/- 0.01 mag,
i' = 18.19 +/- 0.01 mag,
z' = 18.01 +/- 0.01 mag,
J  = 17.66 +/- 0.02 mag,
H  = 17.38 +/- 0.02 mag, and
K  = 17.14 +/- 0.15 mag.

Optical magnitudes are calibrated against the Pan-STARRS catalog,
NIR magnitudes against 2MASS stars in the field.

After correcting for a Galactic foreground reddening of E(B-V)=0.09
mag (Schlegel et al. 1998), the SED is a power-law with no evidence
for extinction by dust in the GRB host galaxy.

We thank Sam Kim for excellent support and for performing the
observations.


GRB_name: GRB210731A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30576
SUBJECT: GRB 210731A: Swift-XRT refined Analysis
DATE:    21/08/01 17:24:27 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), 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), D.N. Burrows (PSU) and E. Troja report on behalf of the
Swift-XRT team:

We have analysed 7.9 ks of XRT data for GRB 210731A (Troja et al. GCN
Circ. 30568), from 191 s to 60.1 ks after the  BAT trigger. The data
comprise 62 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 3002 s of PC mode data and 8 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 = 300.30466, -28.06096
which is equivalent to:

RA (J2000): 20h 01m 13.12s
Dec(J2000): -28d 03' 39.4"

with an uncertainty of 2.2 arcsec (radius, 90% confidence).

The light curve can be modelled with an initial power-law decay with an
index of alpha=3.6 (+/-0.5), followed by a break at T+424 s to an alpha
of 0.86 (+0.18, -0.19).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 3.07 (+0.29, -0.21). The
best-fitting absorption column is  1.36 (+0.47, -0.21) x 10^21 cm^-2,
consistent with the Galactic value of 1.1 x 10^21 cm^-2 (Willingale et
al. 2013). The PC mode spectrum has a photon index of 1.97 (+0.26,
-0.19) and a best-fitting absorption column of 1.35 (+0.77, -0.20) x
10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum  is 3.4 x 10^-11 (4.3 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.35 (+0.77, -0.20) x 10^21 cm^-2
Galactic foreground: 1.1 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.97 (+0.26, -0.19)

If the light curve continues to decay with a power-law decay index of
0.86, the count rate at T+24 hours will be 0.022 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.3 x
10^-13 (9.3 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/01062336.

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


GRB_name: GRB210801A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30577
SUBJECT: GRB 210801A: BALROG localization (Fermi Trigger 649519043 / GRB 210801581)
DATE:    21/08/01 18:16:08 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
649519043 at 13:57:18 on 01 Aug. 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) = 238.2+/-1.5 deg
Decl.(2000.0) = -40.8+/-0.9 deg
We estimate an additional systematic error of 2 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210801581/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210801581/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210801581/json

                        


GRB_name: GRB210731A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30578
SUBJECT: GRB 210731A: MASTER optical afterglow  detection 
DATE:    21/08/01 18:45:53 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov,  E. Gorbovskoy, N.Tyurina, K.Minkina, I.Gorbunov,
P.Balanutsa,V.Vladimirov, A.Kuznetsov, D.Cheryasov (Lomonosov Moscow State 
University,SAI, Physics Department),
O.A. Gres, N.M. Budnev (Irkutsk State University, API),
R. Podesta, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar
OAFA),

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

D. Buckley (South African Astronomical Observatory),

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

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

A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)

Three MASTER robotic telescopes  (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) in Spain (IAC, Canary) and South Africa (SAAO observatory)   automatically 
observed Swift GRB 210801A (Troja et al., GCN 30568) started 60-70s after 
trigger (Lipunov ) up to 2021-08-01 09:16:46 (Lipunov et al., GCN 30567).


MASTER-OAFA auto-detection system ( Lipunov et al., "MASTER Global Robotic 
Net", Advances in Astronomy, 2010, 30L )
  discovered OT source at (RA, Dec) = 20h 01m 13.07s , -28d 03m 39s.6 
(err = +-0".9).

The OT magnitude in 'clear' filter is 18.3m (mlim = 19.8) at plato ( see 
detection de  Wet et al., GCN 30570).

The OT is seen in dozeens images. There is no minor planet at this place.

We have reference image on 2017-08-22.12663 UT with 'clear' filter 19.7m.


GRB_name: GRB210731A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30580
SUBJECT: GRB 210731A: Swift-BAT refined analysis
DATE:    21/08/01 21:12:47 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

M. Stamatikos (OSU), 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), T. Sakamoto (AGU),
E. Troja (NASA/GSFC/UMCP) T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-239 to T+409 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 210731A (trigger #1062336)
(Troja et al., GCN Circ. 30568).  The BAT ground-calculated position is
RA, Dec = 300.311, -28.056 deg which is
   RA(J2000)  =  20h 01m 14.5s
   Dec(J2000) = -28d 03' 20.0"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 39%.

The mask-weighted light curve shows a single-pulse structure that
starts at ~T-1 s, peaks at ~T+11 s, and ends at ~T+30 s.
T90 (15-350 keV) is 22.51 +- 2.79 sec (estimated error
including systematics).

The time-averaged spectrum from T-0.78 to T+25.50 sec is best fit
by a power law with an exponential cutoff.  This fit gives a photon
index -0.25 +- 0.59, and Epeak of 106.5 +- 26.8 keV (chi squared
50.28 for 56 d.o.f.).  For this model the total fluence in the 15-150 keV
band is 2.2 +- 0.2 x 10^-6 erg/cm2 and the 1-sec peak flux measured
from T+11.28 sec in the 15-150 keV band is 1.6 +- 0.3 ph/cm2/sec.
A fit to a simple power law gives a photon index of 1.01 +- 0.11
(chi squared 67.96 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/1062336/BA/


GRB_name: GRB210731A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30582
SUBJECT: GRB 210731A: KAIT Optical Detection
DATE:    21/08/02 09:19:57 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 210731A (Troja et al.,
GCN 30568) starting at ~9.04 hours after the Swift trigger.
A total of 30x60s images were obtained in the clear (roughly R)
filter. The optical afterglow (de Wet et al., GCN 30571; Kuin et al.,
GCN 30572; Guelbenzu et al., GCN 30574; Lipunov et al., GCN 30578;)
was clearly detected in each single image. We measured its brightness
of 18.6 +/- 0.1 mag at 9.26 hours after burst, calibrated to the
Pan-STARRS1 catalog.


GRB_name: GRB210731A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30583
SUBJECT: GRB 210731A: VLT/X-shooter redshift
DATE:    21/08/02 09:53:24 GMT
FROM:    Andrew Levan at U.of Leicester  <a.levan@astro.ru.nl>

D.A. Kann (HETH/IAA-CSIC), L. Izzo (DARK/NBI), A.J. Levan (Radboud),  D.B. Malesani (DTU Space), S. de Wet (UCT) report for the STARGATE collaboration: 

"We observed the afterglow of GRB 210731A (Troja et al. GCN 30568, de Wet et al. GCN 30570) with the ESO VLT UT3 equipped with the X-shooter spectrograph on 1 Aug 2021. A total of 4800 s (4x1200 s) of spectra were obtained starting at 02:45 UT (approximately 28.5 hours after the burst). 

The afterglow is well detected in the acquisition imaging with r=20.7+/- 0.1, and a continuum is visible across the X-shooter spectral range. The spectra contain several prominent absorption features of Fe II, Al III, Mg II and Mg I, at a common redshift z=1.2525. This is consistent with the detection of the afterglow in all the UVOT filters (Kuin & Troja GCN 30572), and we suggest it to be the redshift of GRB 210731A. 

We thank the Paranal staff for the excellent assistance in securing these observations."


GRB_name: GRB210731A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30584
SUBJECT: GRB 210731A: continued GROND observations
DATE:    21/08/02 15:06:50 GMT
FROM:    Ana Nicuesa at TLS Tautenburg  <ana@tls-tautenburg.de>

A. Nicuesa Guelbenzu, S. Klose, S. Schmidl (all TLS Tautenburg), A. Rau
(MPE Garching), and D. A. Kann (HETH/IAA-CSIC) report:

Using GROND mounted at the 2.2m MPG telescope at ESO La Silla Observatory
(Chile), we continued to observe the bright afterglow of GRB 210731A
(Swift trigger 1062336; Troja et al., GCN 30568).

A comparison of our first-epoch optical data (Nicuesa Guelbenzu et al.,
GCN 30574) with those from de Wet et al. (GCN 30570) indicated that the
optical afterglow underwent a relatively long-lasting plateau phase (see
also Zhen & Filippenko, GCN 30582). Our 2nd epoch GROND observations now
reveal that this plateau phase has finished and the afterglow has entered
a declining phase.

At a mean time of 1.22 days post burst we measure (AB magnitudes)

r' = 20.74 +/- 0.02 mag,

calibrated against the Pan-STARRS catalog. This is in good agreement with
the VLT X-shooter result at 1.19 d (Kann et al., GCN 30583).


We thank Sam Kim for excellent support and for performing the
observations.


GRB_name: GRB210801A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30585
SUBJECT: GRB 210801A: Fermi GBM detection
DATE:    21/08/02 15:53:21 GMT
FROM:    Oliver J Roberts at USRA/NASA  <oliver.roberts@nasa.gov>

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

"At 13:57:18.60 UT on 01 August 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210801A (trigger 649519043 / 210801581).

The on-ground calculated location, using the GBM trigger data, is 
RA = 252.77, DEC = -45.82 (J2000 degrees, 
equivalent to 16 h 51 m, -45 d 49 '), with a statistical uncertainty
of 1.6 degrees (radius, 1-sigma containment, statistical only; there is 
additionally a systematic error which we have characterized as a 
core-plus-tail model, with 90% of GRBs having a 3.7 deg error and a small 
tail suffering a larger than 10 deg systematic error. 
[Connaughton et al. 2015, ApJS, 216, 32] ).

The angle from the Fermi LAT boresight at the GBM trigger time is 120 degrees.

The GBM light curve shows two pulses (the second is much brighter than the 
first), with a duration (T90) of about 14 s (50-300 keV). The time-averaged 
spectrum from T0-0.2 s to T0+13.4 s is best fit by a Band function with 
Epeak = 41.8 +/- 1.5 keV, alpha = -1.51 +/- 0.05, and beta = -2.98 +/- 0.3.

A power law function with an exponential high-energy cutoff fits the spectrum 
equally well with a power law index of -1.56 +/- 0.04 and a cutoff energy, 
parameterized as Epeak, of 43.0 +/- 1.5 keV

The event fluence (10-1000 keV) in this time interval is
(1.44 +/- 0.04)E-05  erg/cm^2. The 1-sec peak photon flux measured
starting from T0+10.3 s in the 10-1000 keV band is 70 +/- 1 ph/s/cm^2.

We note that the position of this burst lies along the galactic plane.

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: GRB210802A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30587
SUBJECT: GRB 210802A: Tiled Swift observations
DATE:    21/08/03 07:42:50 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 series of observations, tiled on the sky, of the
Fermi/LAT GRB 210802A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00100

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of finding
serendipitous sources, unrelated to the Fermi/LAT event is high: 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: GRB210803A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30588
SUBJECT: GRB 210803A: BALROG localization (Fermi Trigger 649684549 / GRB 210803497)
DATE:    21/08/03 12:21:12 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
649684549 at 11:55:44 on 03 Aug. 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) = 202.4+/-0.4 deg
Decl.(2000.0) = -33.9+/-0.7 deg
We estimate an additional systematic error of 2 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210803497/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210803497/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210803497/json

                        


GRB_name: GRB210802A
Detection_method: Fermi LAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30589
SUBJECT: GRB 210802A: Fermi-LAT detection
DATE:    21/08/03 13:12:38 GMT
FROM:    Magnus Axelsson at Stockholm U.  <magaxe@kth.se>

F. Longo (University and INFN, Trieste), M. Arimoto (Kanazawa Univ.), E. Bissaldi (Politecnico and INFN, Bari), M. Axelsson (KTH & Stockholm Univ.) and M. Ohno (Hiroshima Univ. & EÃ¶tvÃ¶s Univ.) report on behalf of the Fermi-LAT Collaboration:

On 2 August 2021, Fermi-LAT detected high-energy emission from GRB 210802A which was also detected by Fermi-GBM (trigger 649627691/210802839). The best LAT on-ground location is found to be

RA, Dec = 230.9, 29.8 (degrees, J2000)

with an error radius of 0.35 deg (90% containment, statistical error only). This was 51 deg from the LAT boresight at the time of the GBM trigger:

T0 = 20:08:06.49 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 with high significance.

The photon flux above 100 MeV in the time interval 0-1000 s after the GBM trigger is (1.0 +/- 0.3) E-5 ph/cm2/s.
The estimated photon index above 100 MeV is -2.3 +/- 0.3.
The highest-energy photon is a 1.4 GeV event which is observed 3 seconds after the GBM trigger.

A Swift ToO has been approved for this burst.

The Fermi-LAT point of contact for this burst is Elisabetta Bissaldi (elisabetta.bissaldi@ba.infn.it<mailto:elisabetta.bissaldi@ba.infn.it>).

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: GRB210802A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30590
SUBJECT: GRB 210802A: Fermi GBM detection
DATE:    21/08/03 14:58:46 GMT
FROM:    Oliver J Roberts at USRA/NASA  <oliver.roberts@nasa.gov>

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

"At 20:08:06.49 UT on 02 August 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210802A (trigger 649627691 / 210802839), which was 
also detected by Fermi-LAT (F. Longo et al. 2021, GCN 30589).
The Fermi GBM on-ground location is consistent with the LAT position.

The angle from the Fermi LAT boresight at the GBM trigger time is 51 degrees.

The GBM light curve consists of multiple bright pulses
with a duration (T90) of about 11 s (50-300 keV).
The time-averaged spectrum from T0-0.3 s to T0+12.8 s is
well fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.66 +/- 0.02 and
the cutoff energy, parameterized as Epeak, is 372 +/- 12 keV.

The event fluence (10-1000 keV) in this time interval is
(2.10 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+6.6 s in the 10-1000 keV band
is 16.4 +/- 0.3 ph/s/cm^2.

A Band function fits the spectrum equally well
with Epeak= 365 +/- 15 keV, alpha = -0.65 +/- 0.03 and beta = -3.22 +/- 0.75.

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: GRB210802A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30591
SUBJECT: GRB 210802A: Swift-XRT afterglow detection
DATE:    21/08/03 19:23:02 GMT
FROM:    Valerio D'Elia at ASDC  <valerio.delia@ssdc.asi.it>

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

Swift-XRT has performed follow-up observations of the
Fermi/LAT-detected burst GRB 210802A (Longo et al. GCN Circ. 30589) in
a series of observations tiled on the sky. The total exposure time is
5.2 ks, distributed over 4 tiles; the maximum exposure at a single sky
location was 2.3 ks. The data were collected between T0+41.7 ks and
T0+43.0 ks, and are entirely in Photon Counting (PC) mode. 

Twenty-eight uncatalogued X-ray sources are detected. Many of these
sources are in the bottom tile (likely a high background effect), and
in the left tile (possibly an extended emission related to a nearby
cluster of galaxies). One of the most significant sources ("Source 7")
is above the 2SXPS 3-sigma upper limit at this position, and is
therefore likely the GRB afterglow. Using 1246 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 = 230.72285, +29.90180 which is equivalent to:

RA (J2000): 15h 22m 53.48s
Dec(J2000): +29d 54' 06.5"

with an uncertainty of 3.5 arcsec (radius, 90% confidence). This
position is 9.8 arcmin from the Fermi/LAT position.  While we cannot
determine at the present time whether the source is fading, we note
that a previous 1 ks Swift-XRT visit of the field showed no sign of
Source 7 (https://www.swift.ac.uk/2SXPS/Fields/10000004351).

The results of the XRT-team automatic analysis of the likely afterglow
are at https://www.swift.ac.uk/xrt_products/TILED_GRB00100/Source7.php.

The results of the full analysis of the tiled XRT observations are
available at https://www.swift.ac.uk/xrt_products/TILED_GRB00100.

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


GRB_name: GRB210802A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30592
SUBJECT: GRB 210802A: BOOTES-2/TELMA optical upper limit
DATE:    21/08/03 22:25:19 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 (IAA-CSIC), C. Perez del Pulgar, A. Castellon, I. Carrasco (Univ. de Malaga), R. Fernandez-Munoz (IHSM/UMA-CSIC) and M. Jelinek (ASU-CAS), on behalf of a larger collaboration, report:

Following the Fermi trigger of GRB 210802A (Longo GCNC 30589, Roberts et al. GCNC 30590), we triggered the 60cm BOOTES-2/TELMA robotic telescope at IHSM La Mayora (UMA-CSIC) in Algarrobo Costa (Malaga, Spain) after the twilight as soon as it was possible. Useful images were taken only after 20:12 UT on 03 Aug (~1 day after trigger). In the co-added 12 x 60 s exposure image (clear filter), no optical afterglow is detected within the X-ary afterglow position reported by XRT/Swift (Sbarufatti et al. GCNC 30591) down to 20.3 mag.

We thank the staff at La Mayora for its excellent support.


GRB_name: GRB210802A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30593
SUBJECT: GRB 210802A: DDOTI Upper Limits 
DATE:    21/08/04 00:14:44 GMT
FROM:    Alan M Watson at UNAM  <alan@astro.unam.mx>

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

We observed the field of the Fermi GBM/LAT event GRB 210802A (Longo et al., GCN
Circ., 30589; Roberts et al., GCN Circ., 30590) with the DDOTI wide-field imager
at the Observatorio AstronÃ³mico Nacional on Sierra San Pedro Martir (
http://ddoti.astroscu.unam.mx) from 2021-08-03 03:35 to 07:37 UTC (7.45 to 11.48
hours after the trigger).

We observed a region of about 14 degrees in RA by 10 degrees in declination,
with a 1 x 2 grid of pointings centered on the Fermi GBM Final Position
15:19:40.80 +30:18:00.0 (J2000) and including the entire LAT uncertainty region
(Longo et al., GCN Circ., 30589). We obtained about 105 minutes exposure on the
LAT uncertainty region. We obtained AB photometry by calibration against the
APASS catalog.

Comparing to the Pan-STARRS DR1 catalog, we detect no uncatalogued point sources
in the LAT uncertainty region to a 10-sigma limiting magnitude of w = 21.0.

At the position of the candidate X-ray afterglow (Sbarufatti et al., GCN Circ.,
30591), we detect no point source to a 5-sigma limiting magnitude of w = 21.8.

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


GRB_name: GRB210803A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30595
SUBJECT: GRB 210803A: Fermi GBM observation
DATE:    21/08/04 09:07:17 GMT
FROM:    Elisabetta Bissaldi at INFN,Bari  <elisabetta.bissaldi@ba.infn.it>

E. Bissaldi (Politecnico and INFN Bari) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:


"At 11:55:44.40 UT on 3 August 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210803A (trigger 649684549 / 210803497).
The on-ground calculated location, using the GBM trigger data, is

RA = 218.7, DEC = -21.4

(J2000 degrees, equivalent to 14h 34m, -21d 24'),
with a statistical uncertainty of 1 degree (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which we have characterized as a core-plus-tail model, with 90% of
GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg
systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ).

The angle from the Fermi LAT boresight
at the GBM trigger time is 98 degrees.

The GBM light curve consists of bright, FRED-like emission episode
with a duration (T90) of about 9 s (50-300 keV).
The time-averaged spectrum from T0 to T0+9 s is
well fit by a Band function with Epeak = 164 +/- 19 keV,
alpha = -1.20 +/- 0.05, and beta = -2.06 +/- 0.07.

The event fluence (10-1000 keV) in this time interval is
(1.28 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0.4 s in the 10-1000 keV band
is 35.7 +/- 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: GRB210802A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30596
SUBJECT: GRB 210802A: MITSuME Okayama optical upper limits
DATE:    21/08/04 12:26:45 GMT
FROM:    Ryohei Hosokawa at Tokyo Institute of Technology  <hosokawa@hp.phys.titech.ac.jp>

R. Hosokawa, N. Ito, Y. Imai, K. L. Murata, M. Niwano, H. Takamatsu,
R. Noto, S. Sato, M. Takaku, R. Yamaguchi, Y. Yatsu, and N. Kawai
(TokyoTech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 210802A (V. Lipunov et al. GCN Circular
#30586, P. A. Evans et al. GCN Circular #30587, F. Longo et al. GCN
Circular #30589, O.J. Roberts et al. GCN Circular #30590, B.
Sbarufatti et al. GCN Circular #30591, Y.-D. Hu et al. GCN Circular
#30592, Alan M. Watson et al. GCN Circular #30593) with the optical
three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm
telescope Okayama. The observation with a series of 60 sec exposures
started at 2021-08-03 10:34:24 UT (14.4 hours after Fermi trigger). We
stacked the images with good conditions. We did not detect any
uncatalogued sources within the XRT error region (B. Sbarufatti et al.
GCN Circular #30591). We obtained the 5-sigma limits of the stacked
images as follows.

T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
15.8 2021-08-03 11:54:24 1080 Rc>17.2, Ic>16.9
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time

We used 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: GRB210807A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30600
SUBJECT: GRB 210807A: Swift detection of a burst with an optical counterpart
DATE:    21/08/07 10:34:25 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

A. Y. Lien (GSFC/UMBC), C. Gronwall (PSU), J.D. Gropp (PSU),
N. J. Klingler (GSFC/UMBC/CRESSTII), K. L. Page (U Leicester) and
D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 10:03:40 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210807A (trigger=1064221).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 76.677, +58.245 which is 
   RA(J2000) = 05h 06m 43s
   Dec(J2000) = +58d 14' 43"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty). Because this is an image trigger,
the actual light curve structure requires further ground 
data analysis. The 112-s image trigger indicates that 
this is a long burst. 

The XRT began observing the field at 10:07:02.3 UT, 201.9 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 76.6815, 58.2503 which is equivalent to:
   RA(J2000)  = 05h 06m 43.56s
   Dec(J2000) = +58d 15' 01.1"
with an uncertainty of 11.1 arcseconds (radius, 90% containment). This
location is 20 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy. 

The initial flux in the 2.5 s image was 4.08e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 210 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  = 05:06:43.90 =  76.68293
  DEC(J2000) = +58:14:59.2  =  58.24978
with a 90%-confidence error radius of about 0.61 arc sec. This position is 3.3
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.00 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.409. 

Burst Advocate for this burst is A. Y. Lien (amy.y.lien 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: GRB210807B
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30601
SUBJECT: GRB 210807B: Fermi GBM Final Real-time Localization
DATE:    21/08/07 12:47:05 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 12:36:42 UT on 7 Aug 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210807B (trigger 650032607.844228 / 210807525).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 256.2, Dec = -32.2 (J2000 degrees, equivalent to J2000 17h 04m, -32d 12'), with a statistical uncertainty of 3.8 degrees.

The angle from the Fermi LAT boresight is 19.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210807525/quicklook/glg_skymap_all_bn210807525.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/bn210807525/quicklook/glg_healpix_all_bn210807525.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210807525/quicklook/glg_lc_medres34_bn210807525.gif


GRB_name: GRB210807A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30602
SUBJECT: GRB 210807A: BOOTES-5/JGT optical afterglow detection
DATE:    21/08/07 14:09:06 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

Y.-D. Hu, T.-R. Sun, E. Fernandez-Garcia and A. J. Castro-Tirado, M.D. Caballero-Garcia (IAA-CSIC), D. Hiriart and W. H. Lee (UNAM), C. J. Perez del Pulgar and I. Carrasco (UMA), I. H. Park (SKKU) on behalf of a larger collaboration, report:

The 60cm BOOTES-5/JGT robotic telescope at Observatorio Astronomico Nacional in San Pedro Martir (Mexico) automatically responded in 16 min to the Swift trigger of GRB 210807A (Lien et al., GCNC 30600). The first image (1s exposure, clear-filter) was obtained at 10:20:19.5 UT. We detected the optical afterglow at the position reported by Swift /UVOT (Lien et al. GCNC 30600). In the co-added image (10 x 1s exposures) we measure 17.8+/- 0.2 mag. Further analysis is ongoing. The magnitude is calibrated against the USNO-B1 catalog and is not corrected for Galactic extinction in the direction towards the GRB.

We thank the staff at Observatorio Astronomico Nacional in San Pedro Martir for its excellent support.


GRB_name: GRB210807A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30603
SUBJECT: GRB 210807A: Enhanced Swift-XRT position
DATE:    21/08/07 16:09:23 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 1337 s of XRT Photon Counting mode data and 4 UVOT
images for GRB 210807A, 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 = 76.68376, +58.24980 which is equivalent
to:

RA (J2000): 05h 06m 44.10s
Dec (J2000): +58d 14' 59.3"

with an uncertainty of 2.1 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: GRB210807A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30607
SUBJECT: Swift GRB 210807A: Global MASTER-Net observations report 
DATE:    21/08/07 20:08:23 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-Tavrida robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the Swift GRB 210807A ( A. Y. Lien et al., GCN 30600) errorbox  32639 sec after notice time and 33871 sec after trigger time at 2021-08-07 19:28:12 UT, with upper limit up to  16.6 mag. The observations began at zenith distance = 76 deg. The sun  altitude  is -21.7 deg. 

The galactic latitude b = 11 deg., longitude l = 152 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1683291

We obtain a following upper limits.  

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

   33962 |      MASTER-Tavrida |   C |   180 | 13.4 |        
   35859 |      MASTER-Tavrida |   C |   180 | 16.6 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210807B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30608
SUBJECT: Fermi GRB 210807B: Global MASTER-Net observations report 
DATE:    21/08/07 21:30:37 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 210807B ( Fermi GBM team, GCN 30601) errorbox  28908 sec after notice time and 28937 sec after trigger time at 2021-08-07 20:38:59 UT, with upper limit up to  18.0 mag. Observations started at twilight.  The observations began at zenith distance = 60 deg. The sun  altitude  is -11.2 deg. 

The galactic latitude b =  5 deg., longitude l = 353 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1683395

We obtain a following upper limits.  

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

   28967 | 2021-08-07 20:38:59 |          MASTER-IAC | (17h 12m 56.82s , -31d 05m 11.5s) |   C |    60 | 16.1 |        
   28967 | 2021-08-07 20:38:59 |          MASTER-IAC | (17h 03m 35.72s , -30d 59m 44.0s) |   C |    60 | 16.0 |        
   29047 | 2021-08-07 20:40:20 |          MASTER-IAC | (17h 16m 35.97s , -33d 00m 24.9s) |   C |    60 | 16.6 |        
   29047 | 2021-08-07 20:40:20 |          MASTER-IAC | (17h 07m 03.20s , -32d 54m 57.0s) |   C |    60 | 16.1 |        
   29127 | 2021-08-07 20:41:40 |          MASTER-IAC | (16h 48m 51.47s , -32d 55m 34.2s) |   C |    60 | 16.6 |        
   29127 | 2021-08-07 20:41:40 |          MASTER-IAC | (16h 58m 24.29s , -33d 01m 02.3s) |   C |    60 | 16.5 |        
   29207 | 2021-08-07 20:43:00 |          MASTER-IAC | (17h 10m 44.02s , -29d 13m 03.7s) |   C |    60 | 16.7 |        
   29207 | 2021-08-07 20:43:00 |          MASTER-IAC | (17h 01m 33.44s , -29d 07m 34.1s) |   C |    60 | 16.6 |        
   29288 | 2021-08-07 20:44:20 |          MASTER-IAC | (17h 02m 55.00s , -34d 53m 40.6s) |   C |    60 | 16.8 |        
   29288 | 2021-08-07 20:44:20 |          MASTER-IAC | (16h 53m 09.59s , -34d 48m 12.6s) |   C |    60 | 16.7 |        
   29368 | 2021-08-07 20:45:40 |          MASTER-IAC | (16h 55m 14.70s , -31d 06m 37.7s) |   C |    60 | 17.1 |        
   29368 | 2021-08-07 20:45:40 |          MASTER-IAC | (16h 45m 53.53s , -31d 01m 08.2s) |   C |    60 | 17.0 |        
   29448 | 2021-08-07 20:47:00 |          MASTER-IAC | (17h 21m 30.81s , -34d 54m 09.6s) |   C |    60 | 18.0 |        
   29448 | 2021-08-07 20:47:00 |          MASTER-IAC | (17h 11m 45.36s , -34d 48m 40.7s) |   C |    60 | 17.3 |        
   29528 | 2021-08-07 20:48:21 |          MASTER-IAC | (16h 53m 13.33s , -29d 12m 07.3s) |   C |    60 | 17.1 |        
   29528 | 2021-08-07 20:48:21 |          MASTER-IAC | (16h 44m 02.70s , -29d 06m 37.9s) |   C |    60 | 17.3 |        
   29608 | 2021-08-07 20:49:41 |          MASTER-IAC | (17h 09m 31.78s , -27d 17m 33.2s) |   C |    60 | 17.2 |        
   29608 | 2021-08-07 20:49:41 |          MASTER-IAC | (17h 00m 30.73s , -27d 12m 02.9s) |   C |    60 | 16.9 |        
   29688 | 2021-08-07 20:51:00 |          MASTER-IAC | (17h 30m 47.18s , -31d 07m 06.4s) |   C |    60 | 17.6 |        
   29688 | 2021-08-07 20:51:00 |          MASTER-IAC | (17h 21m 25.82s , -31d 01m 36.5s) |   C |    60 | 17.1 |        
   29768 | 2021-08-07 20:52:20 |          MASTER-IAC | (17h 08m 42.53s , -36d 49m 32.2s) |   C |    60 | 17.8 |        
   29768 | 2021-08-07 20:52:20 |          MASTER-IAC | (16h 58m 42.55s , -36d 44m 04.1s) |   C |    60 | 17.0 |        
   29848 | 2021-08-07 20:53:40 |          MASTER-IAC | (17h 28m 08.83s , -29d 13m 52.9s) |   C |    60 | 17.3 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210807C
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30609
SUBJECT: GRB 210807C: Fermi GBM Final Real-time Localization
DATE:    21/08/07 23:05:39 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 22:55:24 UT on 7 Aug 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210807C (trigger 650069729.307352 / 210807955).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 147.6, Dec = -51.4 (J2000 degrees, equivalent to J2000 09h 50m, -51d 23'), with a statistical uncertainty of 1.7 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/bn210807955/quicklook/glg_skymap_all_bn210807955.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/bn210807955/quicklook/glg_healpix_all_bn210807955.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210807955/quicklook/glg_lc_medres34_bn210807955.gif


GRB_name: GRB210807C
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30610
SUBJECT: GRB 210807C: Swift detection of a burst
DATE:    21/08/07 23:14:05 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

A. Y. Lien (GSFC/UMBC), C. Gronwall (PSU), J.D. Gropp (PSU),
N. J. Klingler (GSFC/UMBC/CRESSTII), K. L. Page (U Leicester) and
D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 22:57:08 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210807C (trigger=1064421).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 143.551, -51.409 which is 
   RA(J2000) = 09h 34m 12s
   Dec(J2000) = -51d 24' 31"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  Although the lightcurve before T+8s is
not currently available due to a telemetry dropout, the later lightcurve
shows a complex structure extending at least to T+90s.  The peak count 
rate in the available lightcurve was ~800 counts/sec (15-350 keV), 
at ~20 sec after the trigger. 

The XRT began observing the field at 23:00:05.5 UT, 177.1 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 143.53455, -51.40237 which
is equivalent to:
   RA(J2000)  = 09h 34m 08.29s
   Dec(J2000) = -51d 24' 08.5"
with an uncertainty of 7.1 arcseconds (radius, 90% containment). This
location is 43 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. 

A power-law fit to a spectrum formed from promptly downlinked event
data does not constrain the column density. 

The initial flux in the 2.5 s image was 2.31e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 250 seconds with the V filter starting
180 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 19.2 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 18.0 mag. No
correction has been made for the large, but uncertain, extinction expected. 

Burst Advocate for this burst is A. Y. Lien (amy.y.lien 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: GRB210807C
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30612
SUBJECT: Fermi GRB 210807C: Global MASTER-Net observations report 
DATE:    21/08/08 03:30:32 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 210807C ( Fermi GBM team, GCN 30609) errorbox  114 sec after notice time and 206 sec after trigger time at 2021-08-07 22:58:50 UT, with upper limit up to  18.6 mag. Observations started at twilight.  The observations began at zenith distance = 64 deg. The sun  altitude  is -12.1 deg. 

MASTER-SAAO robotic telescope  located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 210807C errorbox  15419 sec after notice time and 15511 sec after trigger time at 2021-08-08 03:13:56 UT, with upper limit up to  17.5 mag. The observations began at zenith distance = 81 deg. The sun  altitude  is -27.5 deg. 

The galactic latitude b =  2 deg., longitude l = 277 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1683879

We obtain a following upper limits.  

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

     222 | 2021-08-07 22:58:50 |         MASTER-OAFA | (09h 51m 36.60s , -48d 08m 16.7s) |   C |    30 | 16.4 |        
     285 | 2021-08-07 22:59:59 |         MASTER-OAFA | (09h 32m 30.94s , -50d 38m 28.4s) |   C |    20 | 16.6 |        
     320 | 2021-08-07 22:59:59 |         MASTER-OAFA | (09h 32m 30.95s , -50d 38m 28.4s) |   C |    90 | 17.3 |  Coadd 
     615 | 2021-08-07 22:59:59 |         MASTER-OAFA | (09h 32m 30.93s , -50d 38m 28.5s) |   C |   680 | 18.3 |  Coadd 
     330 | 2021-08-07 23:00:39 |         MASTER-OAFA | (09h 32m 26.75s , -50d 36m 58.8s) |   C |    30 | 16.8 |        
     384 | 2021-08-07 23:01:28 |         MASTER-OAFA | (09h 32m 26.54s , -50d 38m 17.9s) |   C |    40 | 17.0 |        
     449 | 2021-08-07 23:02:28 |         MASTER-OAFA | (09h 32m 28.68s , -50d 37m 04.2s) |   C |    50 | 17.1 |        
     524 | 2021-08-07 23:02:28 |         MASTER-OAFA | (09h 32m 28.68s , -50d 37m 04.3s) |   C |   200 | 17.8 |  Coadd 
     528 | 2021-08-07 23:03:37 |         MASTER-OAFA | (09h 32m 22.55s , -50d 37m 43.5s) |   C |    70 | 17.3 |        
     622 | 2021-08-07 23:05:06 |         MASTER-OAFA | (09h 32m 22.46s , -50d 36m 42.4s) |   C |    80 | 17.5 |        
     732 | 2021-08-07 23:06:46 |         MASTER-OAFA | (09h 32m 28.12s , -50d 37m 41.4s) |   C |   100 | 17.7 |        
     877 | 2021-08-07 23:06:46 |         MASTER-OAFA | (09h 32m 28.14s , -50d 37m 41.5s) |   C |   390 | 18.3 |  Coadd 
     866 | 2021-08-07 23:08:45 |         MASTER-OAFA | (09h 32m 22.16s , -50d 38m 40.7s) |   C |   130 | 17.9 |        
    1030 | 2021-08-07 23:11:14 |         MASTER-OAFA | (09h 32m 29.66s , -50d 38m 09.7s) |   C |   160 | 18.0 |        
    1220 | 2021-08-07 23:14:14 |         MASTER-OAFA | (09h 32m 25.67s , -50d 37m 04.8s) |   C |   180 | 18.2 |        
    1400 | 2021-08-07 23:14:14 |         MASTER-OAFA | (09h 32m 25.67s , -50d 37m 04.8s) |   C |   540 | 18.6 |  Coadd 
    1420 | 2021-08-07 23:17:34 |         MASTER-OAFA | (09h 32m 25.60s , -50d 38m 34.9s) |   C |   180 | 18.2 |        
    1619 | 2021-08-07 23:20:53 |         MASTER-OAFA | (09h 32m 28.21s , -50d 36m 47.5s) |   C |   180 | 18.3 |        
    1819 | 2021-08-07 23:24:13 |         MASTER-OAFA | (09h 32m 22.92s , -50d 37m 36.2s) |   C |   180 | 18.2 |        
    1999 | 2021-08-07 23:24:13 |         MASTER-OAFA | (09h 32m 22.92s , -50d 37m 36.2s) |   C |   540 | 18.6 |  Coadd 
    2019 | 2021-08-07 23:27:32 |         MASTER-OAFA | (09h 32m 22.25s , -50d 36m 35.5s) |   C |   180 | 18.3 |        
    2218 | 2021-08-07 23:30:52 |         MASTER-OAFA | (09h 32m 28.88s , -50d 37m 34.8s) |   C |   180 | 18.3 |        
    2417 | 2021-08-07 23:34:11 |         MASTER-OAFA | (09h 32m 22.28s , -50d 38m 34.3s) |   C |   180 | 18.2 |        
    2597 | 2021-08-07 23:34:11 |         MASTER-OAFA | (09h 32m 22.29s , -50d 38m 34.3s) |   C |   540 | 18.6 |  Coadd 
    2617 | 2021-08-07 23:37:31 |         MASTER-OAFA | (09h 32m 29.11s , -50d 38m 18.2s) |   C |   180 | 18.2 |        
    2816 | 2021-08-07 23:40:50 |         MASTER-OAFA | (09h 32m 25.11s , -50d 36m 58.5s) |   C |   180 | 18.3 |        
    3016 | 2021-08-07 23:44:09 |         MASTER-OAFA | (09h 32m 25.02s , -50d 38m 21.0s) |   C |   180 | 18.3 |        
    3196 | 2021-08-07 23:44:09 |         MASTER-OAFA | (09h 32m 25.02s , -50d 38m 21.0s) |   C |   540 | 18.5 |  Coadd 
    3215 | 2021-08-07 23:47:29 |         MASTER-OAFA | (09h 32m 28.03s , -50d 36m 52.9s) |   C |   180 | 18.2 |        
    3415 | 2021-08-07 23:50:49 |         MASTER-OAFA | (09h 32m 21.71s , -50d 37m 32.1s) |   C |   180 | 18.2 |        
    3614 | 2021-08-07 23:54:08 |         MASTER-OAFA | (09h 32m 21.47s , -50d 36m 31.4s) |   C |   180 | 18.1 |        
    3794 | 2021-08-07 23:54:08 |         MASTER-OAFA | (09h 32m 21.47s , -50d 36m 31.5s) |   C |   540 | 18.5 |  Coadd 
    3814 | 2021-08-07 23:57:27 |         MASTER-OAFA | (09h 32m 27.57s , -50d 37m 32.7s) |   C |   180 | 17.9 |        
    4013 | 2021-08-08 00:00:47 |         MASTER-OAFA | (09h 32m 20.35s , -50d 38m 40.0s) |   C |   180 | 18.1 |        
    4212 | 2021-08-08 00:04:06 |         MASTER-OAFA | (09h 32m 27.14s , -50d 38m 22.6s) |   C |   180 | 18.1 |        
    4392 | 2021-08-08 00:04:06 |         MASTER-OAFA | (09h 32m 27.14s , -50d 38m 22.6s) |   C |   540 | 18.5 |  Coadd 
    4412 | 2021-08-08 00:07:26 |         MASTER-OAFA | (09h 32m 23.81s , -50d 36m 49.8s) |   C |   180 | 18.1 |        
    4612 | 2021-08-08 00:10:46 |         MASTER-OAFA | (09h 32m 23.52s , -50d 38m 37.4s) |   C |   180 | 18.1 |        
    4811 | 2021-08-08 00:14:05 |         MASTER-OAFA | (09h 32m 25.80s , -50d 36m 50.7s) |   C |   180 | 18.1 |        
    5330 | 2021-08-08 00:22:44 |         MASTER-OAFA | (09h 32m 23.46s , -50d 36m 07.4s) |   C |   180 | 17.6 |        
    5847 | 2021-08-08 00:31:20 |         MASTER-OAFA | (09h 32m 22.91s , -50d 38m 05.8s) |   C |   180 | 17.5 |        
    6366 | 2021-08-08 00:40:00 |         MASTER-OAFA | (09h 32m 21.93s , -50d 36m 57.0s) |   C |   180 | 17.2 |        
    6884 | 2021-08-08 00:48:38 |         MASTER-OAFA | (09h 32m 25.05s , -50d 36m 50.2s) |   C |   180 | 17.2 |        
    7402 | 2021-08-08 00:57:16 |         MASTER-OAFA | (09h 32m 16.96s , -50d 36m 40.0s) |   C |   180 | 16.9 |        
    7921 | 2021-08-08 01:05:55 |         MASTER-OAFA | (09h 32m 16.80s , -50d 38m 40.1s) |   C |   180 | 16.7 |        
    8437 | 2021-08-08 01:14:31 |         MASTER-OAFA | (09h 32m 17.73s , -50d 36m 54.2s) |   C |   180 | 16.6 |        
    8956 | 2021-08-08 01:23:10 |         MASTER-OAFA | (09h 32m 20.07s , -50d 36m 39.2s) |   C |   180 | 16.1 |        
    9475 | 2021-08-08 01:31:49 |         MASTER-OAFA | (09h 32m 10.94s , -50d 36m 17.5s) |   C |   180 | 14.0 |        
   15602 | 2021-08-08 03:13:56 |         MASTER-SAAO | (09h 34m 22.59s , -51d 21m 56.9s) |   C |   180 | 17.5 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210610B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30614
SUBJECT: GRB 210610B: Assy optical observations
DATE:    21/08/08 05:33:17 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

V. Kim (FAI, Pulkovo Observatory), A. Pozanenko (IKI), M. Krugov (FAI), 
  N. Pankov (HSE, IKI),  S. Belkin (IKI) report on behalf of GRB IKI FuN:

We observed the field of  GRB 210610B (Lien et al., GCN 30600) with 
AZT-20 telescope of Assy-Turgen observatory starting on 2021-08-07 (UT) 
20:45:22.

We clearly detect the optical afterglow (Lien et al., GCN 30600; Hu et 
al., GCN 30602; Lipunov et al., GCN 30607).

Preliminary photometry of the optical afterglow in a stacked image is 
following

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

2021-08-07 20:45:22  0.47601    75*60   r'      21.28  0.05   23.6

The photometry is based on nearby PS1 stars.


GRB_name: GRB210807C
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30615
SUBJECT: GRB 210807C: Enhanced Swift-XRT position
DATE:    21/08/08 07:13:18 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 722 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 210807C, 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 = 143.53386, -51.40105 which is equivalent
to:

RA (J2000): 09h 34m 8.13s
Dec (J2000): -51d 24' 03.8"

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: GRB210807A
Detection_method: correction
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30616
SUBJECT: GRB 210807A: correction to the GCN Circ. #30614 Assy optical observations
DATE:    21/08/08 10:25:45 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

V. Kim (FAI, Pulkovo Observatory), A. Pozanenko (IKI), M. Krugov (FAI),
N. Pankov (HSE, IKI), S. Belkin (IKI) report on behalf of GRB IKI FuN:

The name of  GRB was indicated incorrectly in GCN Circ. #30614.
The observation and photometry in  GCN Circ. #30614 indeed refer to the 
GRB 210807A.

We apologize for possible inconvenience.


GRB_name: GRB210807A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30617
SUBJECT: GRB 210807A: Swift-XRT refined Analysis
DATE:    21/08/08 12:24:18 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), D.N. Burrows (PSU), J. D. Gropp (PSU), J.A.
Kennea (PSU) and A.Y. Lien report on behalf of the Swift-XRT team:

We have analysed 3.1 ks of XRT data for GRB 210807A (Lien et al. GCN
Circ. 30600), from 208 s to 86.2 ks after the  BAT trigger. The data
comprise 488 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. 30603).

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=0.71 (+/-0.09). At T+384 s  the decay
steepens to an alpha of 2.8 (+0.7, -0.6). The light curve breaks again
at T+497 s to a decay with alpha=1.02 (+/-0.03),  before a final break
at T+32.3 ks s after which the decay index is 2.1 (+1.0, -0.7).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.82 (+/-0.03). The
best-fitting absorption column is  5.52 (+0.24, -0.23) x 10^21 cm^-2,
in excess of the Galactic value of 3.4 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.71 (+0.15, -0.12)
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 4.6 x 10^-11 (5.9 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      3.4 (+0.6, -0.0) x 10^21 cm^-2
Galactic foreground: 3.4 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.71 (+0.15, -0.12)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01064221.

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


GRB_name: GRB210807A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30618
SUBJECT: GRB 210807A: Swift/UVOT Detection
DATE:    21/08/08 21:07:25 GMT
FROM:    Sam LaPorte at PSU  <sjl5346@psu.edu>

 GRB 210807A: Swift/UVOT Detection

S. J. LaPorte (PSU) and A. Y. Lien (GSFC/UMBC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210807A
210 s after the BAT trigger (Lien et al., GCN Circ. 30600).
A source consistent with the XRT position
(Lien et al. GCN Circ. 30600)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  05:06:43.89 =  76.68289 (deg.)
    Dec (J2000) = +58:14:59.2  =  58.24979 (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

b                        489            683            38        >17.84
u                        639            659            19        >17.04
v                        390            583            39
16.58+-0.25
uvw1                 440            633             38        >17.12
uvw2                 539            721             26        >17.08
white                 234            383           147
16.93+-0.04
white                 234            708           184          17.19+-0.05

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.409 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210807C
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30619
SUBJECT: GRB 210807C: Swift/UVOT Upper Limits
DATE:    21/08/08 21:44:40 GMT
FROM:    Sam LaPorte at PSU  <sjl5346@psu.edu>

 GRB 210807C: Swift/UVOT Upper Limits

S. J. LaPorte (PSU) and A. Y. Lien (GSFC/UMBC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210807C
180 s after the BAT trigger (Lien et al., GCN Circ. 30610).
No optical afterglow consistent with the XRT position
(Lien et al. GCN Circ. 30610)
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 initial exposures
are:

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

v                  180          852          596         >19.4

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 3.076 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210807C
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30620
SUBJECT: GRB 210807C: Fermi GBM detection
DATE:    21/08/08 22:58:37 GMT
FROM:    Suraj Poolakkil at UAH  <sp0076@uah.edu>

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

"At 22:55:24.31 UT on 7 July 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210807C (trigger 650069729 / 210807955)
which was also detected by the Swift/BAT (Lien et al. 2021, GCN 30610).
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 61
degrees.

The GBM light curve consists of multiple peaks followed by some
extended emission with a duration (T90) of about 125 s (50-300 keV).
The time-averaged spectrum from T0 s to T0+94.2 s
is best fit by a Band function, with Epeak = 170 +/- 28 keV,
alpha = -1.08 +/- 0.06  and beta = -1.61 +/- 0.01.

The event fluence (10-1000 keV) in this time interval is
(56.43 +/- 0.54)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+8.64 s in the 10-1000 keV band
is 7.2 +/- 0.3 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: GRB210807C
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30621
SUBJECT: GRB 210807C: Swift-XRT refined Analysis
DATE:    21/08/09 06:57:14 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans (U. Leicester) and A. Y. Lien (GSFC/UMBC) reports on behalf
of the Swift-XRT team:

We have analysed 5.8 ks of XRT data for GRB 210807C (Lien et al. GCN
Circ. 30610), from 183 s to 56.8 ks after the  BAT trigger. The data
comprise 203 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. 30615).

The light curve can be modelled with a power-law decay with a decay
index of alpha=3.11 (+2.96, -0.22), followed by a break at T0+420.7
(+18.1, -165.2) s to a decay of 1.32 (+0.09, -0.07).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.28 (+0.15, -0.14). The
best-fitting absorption column is  4.9 (+/-0.4) x 10^22 cm^-2, in
excess of the Galactic value of 8.5 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.5 (+/-0.6) and a
best-fitting absorption column of 6.0 (+1.8, -1.5) x 10^22 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 7.6 x 10^-11 (4.1 x 10^-10) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      6.0 (+1.8, -1.5) x 10^22 cm^-2
Galactic foreground: 8.5 x 10^21 cm^-2
Excess significance: 5.5 sigma
Photon index:      2.5 (+/-0.6)


The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01064421.

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


GRB_name: GRB210802A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30622
SUBJECT: GRB 210802A: Further Swift/XRT observation and afterglow confirmation
DATE:    21/08/09 13:55:33 GMT
FROM:    Valerio D'Elia at ASDC  <valerio.delia@ssdc.asi.it>

V. D'Elia (ASI-SSDC & INAF-OAR) and S.B. Cenko (GSFC) report on behalf of the Swift-XRT team:


Swift-XRT has performed further follow-up observations of the Fermi burst (Longo et al., GCN Circ. 30589; Roberts et al., GCN Circ. 30590).

The possible afterglow reported in Sbarufatti et al. (GCN Circ. 30591, "source 7") is no longer detected in a 4 ks observation, down to a three sigma upper limit of 4.8E-3 cts/s (corresponding to 1.28E-13 erg/cm^2/s) at the position of the transient. This value is significantly below the previously reported flux value for the candidate, thus confirming â€œsource 7â€ as the afterglow of GRB 210802A.

The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/xrt_curves/00021456/.

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


GRB_name: GRB210807A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30623
SUBJECT: GRB 210807A: Swift-BAT refined analysis
DATE:    21/08/10 01:41:52 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 210807A (trigger #1064221)
(Lien et al., GCN Circ. 30600).  The BAT ground-calculated position is
RA, Dec = 76.666, 58.257 deg which is
   RA(J2000)  =  05h 06m 39.7s
   Dec(J2000) = +58d 15' 25.6"
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 28%.

The BAT light curve showed a complex structure with a duration of about ~200 sec.
T90 (15-350 keV) is 156.30 +- 214.60 sec (estimated error including systematics).

The time-averaged spectrum from -19.544 to 640.052 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.26 +- 0.08.  The fluence in the 15-150 keV band is 9.5 +- 0.4 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+70.52 sec in the 15-150 keV band
is 1.8 +- 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/1064221/BA/


GRB_name: GRB210807A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30624
SUBJECT: GRB 210807A: Detection by GRBAlpha
DATE:    21/08/10 14:37:22 GMT
FROM:    Masanori Ohno at Hiroshima University  <ohno@astro.hiroshima-u.ac.jp>

J. Ripa (Masaryk U.), M. Ohno (Eotvos U./Hiroshima U.), H. Takahashi
(Hiroshima U.),
A. Pal, L. Meszaros, B. Csak (Konkoly Observatory), N. Werner, M. Topinka,
F. Munz,
F. Hroch (Masaryk U.), T. Urbanec, M. Kasal,  A. Povalac (Brno U. of
Technology),
J. Hudec, J. Kapus, M. Frajt (Spacemanic s.r.o), R. Laszlo, M. Koleda
(Needronix s.r.o),
M. Smelko, P. Hanak, P. Lipovsky (Technical U. of Kosice), G. Galgoczi
(Wigner Research Center/Eotvos U.),
Yuusuke Uchida, Helen Poon, H. Matake, N. Uchida (Hiroshima U.), T. Enoto
(Kyoto U.), Zs. Frei (Eotvos U.),
Y. Fukazawa, K. Hirose (Hiroshima U.); S. Hisadomi (Nagoya U.), Y. Ichinohe
(Rikkyo U.),
L. L. Kiss (Konkoly Observatory),  T. Mizuno (Hiroshima U.), K. Nakazawa
(Nagoya U.),
H. Odaka (Univ of Tokyo), K. Torigoe (Hiroshima U.) -- the GRBAlpha
collaboration.

The long duration GRB 210807A (Swift-BAT detection; Lien et al. GCN Circ.
 30600)
was detected by the GRBAlpha 1U CubeSat (Pal et al. Proc. SPIE 2020).
This is the first time that a GRB was observed by a 1U CubeSat dedicated to
gamma-ray burst observations.

The data acquisition started at 10:05:14 UT and the tail part of the prompt
emission, which  consists of multiple peaks,
was observed with a duration of about 80 sec. The 7.3 sigma detection
significance was confirmed at around 10:06:00 UT.

The light curve obtained by GRBAlpha is available here:
https://grbalpha.konkoly.hu/static/share/GRB210807A.pdf

GRBAlpha is a demonstration mission for a future CubeSats constellation
(Werner et al. Proc. SPIE 2018).
The detector of GRBAlpha consists of a 75 x 75 x 5 mm3 CsI scintillator
read out by a SiPM array,
covering the energy range from ~50 keV to ~1000 keV.
GRBAlpha was launched on 2021 March 22 from Baikonur. After its
commissioning phase,
the scientific observations are now under way. To increase the duty cycle
and the downlink rate,
the upgrade of the on-board data acquisition software stack is in progress.
The ground segment is also supported by the radio amateur community and it
takes advantage
of the SatNOGS network for increased data downlink volume.


GRB_name: GRB210807C
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30625
SUBJECT: GRB 210807C: Swift-BAT refined analysis
DATE:    21/08/10 21:58:19 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 210807C (trigger #1064421)
(Lien et al., GCN Circ. 30610).  The BAT ground-calculated position is
RA, Dec = 143.540, -51.409 deg which is
   RA(J2000)  =  09h 34m 09.7s
   Dec(J2000) = -51d 24' 32.8"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 20%.

The BAT light curve showed a complex structure with a duration of about ~100 sec.
T90 (15-350 keV) is 89.97 +- 6.26 sec (estimated error including systematics).

The time-averaged spectrum from T-31.36 to T+78.57 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.65 +- 0.06.  The fluence in the 15-150 keV band is 1.2 +- 0.0 x 10^-05 erg/cm2.
The 1-sec peak photon flux measured from T-24.22 sec in the 15-150 keV band
is 4.0 +- 0.7 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/1064421/BA/


GRB_name: GRB210807A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30628
SUBJECT: GRB 210807A: Tautenburg observations
DATE:    21/08/11 11:37:11 GMT
FROM:    Ana Nicuesa at TLS Tautenburg  <ana@tls-tautenburg.de>

S. Schmidl, A. Nicuesa Guelbenzu, S. Klose, S. Melnikov, B. Stecklum, U.
Laux (all Tautenburg) and J. Greiner (MPE Garching) report:


We observed the field of GRB 210807A (Lien et al., GCN 30600) with the
Tautenburg 1.34m Schmidt telescope equipped with the TAUKAM 6kx6k CCD
camera.

Observations started at 23:19 UT on August 7, about 13 hours after the GRB
trigger. For the optical afterglow (Lien et al., GCN 30600; Hu et al., GCN
30602; LaPorte et al. GCN 30618) we measure the following magnitudes:

r = 21.66 +/- 0.18, at a midtime of August 7, 23:28 UT,
i = 21.25 +/- 0.19, at a midtime of August 8, 01:16 UT,
z = 20.52 +/- 0.19, at a midtime of August 8, 01:26 UT.

Second-epoch observations were performed the following night.
The optical transient was not detected anymore:

r  22.2, at a midtime of August 8, 23:34 UT,
i  22.4, at a midtime of August 9, 00:38 UT,
z  21.2, at a midtime of August 9, 01:20 UT.

Given magnitudes are calibrated against the Pan-STARRS catalogue.


GRB_name: GRB210730A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30629
SUBJECT: GRB 210730A: Tautenburg observations
DATE:    21/08/11 15:15:49 GMT
FROM:    Ana Nicuesa at TLS Tautenburg  <ana@tls-tautenburg.de>

S. Schmidl, A. Nicuesa Guelbenzu, S. Klose, S. Melnikov, B. Stecklum, C.
Hoegner (all Tautenburg) and J. Greiner (MPE Garching) report:

We observed the field of GRB 210730A (Sonbas et al., GCN 30548) with the
Tautenburg 1.34m Schmidt telescope equipped with the TAUKAM 6kx6k CCD
camera.

Observations started at 20:38 UT on July 30, about 15 hours after the GRB
trigger. Consistent with the non-detection of an afterglow candidate by
D'Avanzo et al. (GCN 30560) and Hu et al. (GCN 30563), we do not detect
any new source inside the XRT error circle (Beardmore et al., GCN 30550).
Calibrated against SDSS stars in the field, for any transient we provide
an upper limit of r(AB) > 21.8 mag.


GRB_name: GRB080101A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30630
SUBJECT: GRB 080101A: Fermi GBM Final Real-time Localization
DATE:    21/08/12 00:26:16 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 23:37:06 UT on 1 Jan 2008, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 080101A (trigger 220923427.133782 / 080101984).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 183.7, Dec = 2.4 (J2000 degrees, equivalent to J2000 12h 14m, 2d 23'), with a statistical uncertainty of 6.3 degrees.

The angle from the Fermi LAT boresight is 29.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2008/bn080101984/quicklook/glg_skymap_all_bn080101984.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2008/bn080101984/quicklook/glg_healpix_all_bn080101984.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2008/bn080101984/quicklook/glg_lc_medres34_bn080101984.gif


GRB_name: GRB080102A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30632
SUBJECT: GRB 080102A: Fermi GBM Final Real-time Localization
DATE:    21/08/12 16:57:21 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 16:08:15 UT on 2 Jan 2008, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 080102A (trigger 220982896.414242 / 080102672).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 39.7, Dec = 69.6 (J2000 degrees, equivalent to J2000 02h 38m, 69d 35'), with a statistical uncertainty of 1.1 degrees.

The angle from the Fermi LAT boresight is 149.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2008/bn080102672/quicklook/glg_skymap_all_bn080102672.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2008/bn080102672/quicklook/glg_healpix_all_bn080102672.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2008/bn080102672/quicklook/glg_lc_medres34_bn080102672.gif


GRB_name: GRB210812A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30633
SUBJECT: GRB 210812A: Fermi GBM Final Real-time Localization
DATE:    21/08/12 18:12:27 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 16:47:01 UT on 12 Aug 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210812A (trigger 650479626.014242 / 210812699).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 39.7, Dec = 69.6 (J2000 degrees, equivalent to J2000 02h 38m, 69d 35'), with a statistical uncertainty of 1.1 degrees.

The angle from the Fermi LAT boresight is 149.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210812699/quicklook/glg_skymap_all_bn210812699.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/bn210812699/quicklook/glg_healpix_all_bn210812699.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210812699/quicklook/glg_lc_medres34_bn210812699.gif


GRB_name: GRB210812A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30634
SUBJECT: GRB 210812A: BALROG localization (Fermi Trigger 650479626 / GRB 210812699)
DATE:    21/08/12 18:14:44 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
650479626 at 16:47:01 on 12 Aug. 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) = 62.1+/-4.2 deg
Decl.(2000.0) = 71.7+/-0.8 deg
We estimate an additional systematic error of 1 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210812699/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210812699/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210812699/json

                        


GRB_name: GRB210812B
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30635
SUBJECT: GRB 210812B: Fermi GBM Final Real-time Localization
DATE:    21/08/12 18:21:09 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 00:15:51 UT on 12 Aug 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210812B (trigger 650420156.733782 / 210812011).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 183.7, Dec = 2.4 (J2000 degrees, equivalent to J2000 12h 14m, 2d 23'), with a statistical uncertainty of 6.3 degrees.

The angle from the Fermi LAT boresight is 29.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210812011/quicklook/glg_skymap_all_bn210812011.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/bn210812011/quicklook/glg_healpix_all_bn210812011.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210812011/quicklook/glg_lc_medres34_bn210812011.gif


GRB_name: GRB210812A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30636
SUBJECT: Fermi GRB 210812A: Global MASTER-Net observations report 
DATE:    21/08/12 19:15:10 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-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 210812A ( Fermi GBM team, GCN 30633) errorbox  3906 sec after notice time and 3934 sec after trigger time at 2021-08-12 17:52:35 UT, with upper limit up to  18.0 mag. Observations started at twilight.  The observations began at zenith distance = 63 deg. The sun  altitude  is -15.8 deg. 

MASTER-Tavrida robotic telescope  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 210812A errorbox  3968 sec after notice time and 3996 sec after trigger time at 2021-08-12 17:53:37 UT, with upper limit up to  16.9 mag. Observations started at twilight.  The observations began at zenith distance = 63 deg. The sun  altitude  is -10.7 deg. 

The galactic latitude b =  9 deg., longitude l = 132 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1688546

We obtain a following upper limits.  

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

    3965 | 2021-08-12 17:52:35 |   MASTER-Kislovodsk | (02h 39m 39.55s , +67d 43m 23.0s) |   C |    60 | 17.1 |        
    3965 | 2021-08-12 17:52:35 |   MASTER-Kislovodsk | (02h 49m 52.81s , +67d 17m 41.9s) |   C |    60 | 18.0 |        
    4027 | 2021-08-12 17:53:37 |      MASTER-Tavrida | (03h 00m 15.85s , +69d 33m 20.0s) |   C |    60 | 14.1 |        
    4045 | 2021-08-12 17:53:56 |   MASTER-Kislovodsk | (02h 23m 17.82s , +71d 30m 31.7s) |   C |    60 | 16.6 |        
    4045 | 2021-08-12 17:53:56 |   MASTER-Kislovodsk | (02h 35m 30.22s , +71d 04m 38.3s) |   C |    60 | 17.6 |        
    4250 | 2021-08-12 17:57:21 |      MASTER-Tavrida | (02h 16m 36.54s , +69d 38m 13.4s) |   C |    60 | 14.2 |        
    4866 | 2021-08-12 18:07:37 |      MASTER-Tavrida | (02h 37m 13.34s , +69d 37m 48.2s) |   C |    60 | 16.1 |        
    4927 | 2021-08-12 18:08:37 |   MASTER-Kislovodsk | (02h 39m 44.39s , +67d 43m 18.2s) |   C |    60 | 17.1 |        
    4927 | 2021-08-12 18:08:37 |   MASTER-Kislovodsk | (02h 50m 00.20s , +67d 17m 36.6s) |   C |    60 | 18.0 |        
    5175 | 2021-08-12 18:12:46 |      MASTER-Tavrida | (02h 16m 39.00s , +69d 38m 21.4s) |   C |    60 | 13.4 |        
    6543 | 2021-08-12 18:35:34 |      MASTER-Tavrida | (02h 37m 17.68s , +69d 39m 33.3s) |   C |    60 | 13.5 |        
    6623 | 2021-08-12 18:36:53 |      MASTER-Tavrida | (03h 00m 13.68s , +69d 36m 38.3s) |   C |    60 | 16.2 |        
    6781 | 2021-08-12 18:39:31 |      MASTER-Tavrida | (02h 16m 35.36s , +69d 40m 00.6s) |   C |    60 | 16.9 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210807A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30637
SUBJECT: GRB 210807A: continued Assy, AbAO and Mondy observations
DATE:    21/08/12 19:34:29 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI),  A. Pozanenko (IKI), V. Kim (FAI, Pulkovo Observatory), 
  R. Ya. Inasaridze (AbAO), E. Klunko (ISTP),  M. Krugov (FAI), N. 
Pankov (HSE),  D. Datashvili (AbAO), V. R. Ayvazian (AbAO),  G. V. 
Kapanadze (AbAO)  report on behalf of IKI GRB FuN:

We continued observation of the GRB 210807A (Lien et al., GCN 30600; 
Ripa  et al., GCN 30624) with AZT-20 of Assy observatory, AZT-33IK of 
Mondy observatory,  and AS-32 of Abastumani observatory.

The optical transient GRB 210807A (Lien et al., GCN 30600; Hu et al., 
GCN 30602; Lipunov et al., GCN 30607; Kim et al., GCNs 30614, 30616; 
LaPorte et al., GCN 30618; Schmidl et al., GCN 30628) was detected in 
almost all of our stacked images. Preliminary photometric results are 
presented below:

Date       UT start  t-T0     Filter Exp.   OT    Err.  UL(3sig) Observ.
                      (mid, days)        (s)
2021-08-07 23:46:09  0.58957   R     53*60  20.94 0.09 21.6    AbAO
2021-08-09 17:11:54  2.31822   R     30*120 22.6  0.35 22.5    Mondy
2021-08-10 17:22:17  3.32334   R     27*120 n/d   n/d  22.7    Mondy
2021-08-10 21:33:07  3.50135   r(AB) 65*60  23.14 0.26 23.7    Assy


The photometry is based on the nearby stars of the USNO-B1.0 catalog.
USNO-B1.0_id R2
1482-0188929 16.72
1482-0188954 15.47
1482-0189006 15.38

and based on the same stars presented in PS1 catalog for r(AB) calibrations.

The light curve plotted based on available data for can be found at

http://grb.rssi.ru/GRB210807A/GRB210807A_LC.png

The light curve can be approximated by broken power law with power law 
indices of -0.55 and -1.05 before and after break at about 0.22 days.


GRB_name: GRB210812B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30638
SUBJECT: Retraction of Fermi GBM GCN 30630 and GCN 30632
DATE:    21/08/12 21:43:37 GMT
FROM:    Peter Veres at UAH  <veresp@gmail.com>

The Fermi GBM Team reports:

"
Due to a data processing error, the names of two GRBs localized by Fermi
GBM were incorrectly reported in GCN 30630 and GCN 30632.

The error was corrected and the final real-time localizations of these GRBs
were re-sent in two new GCNs. The correction for GCN 30630 was sent as GCN
30635 with the name GRB 210812B. The correction for GCN 30632 was sent as
GCN 30633 with the name GRB 210812A.

We apologize for any confusion this may have caused."


GRB_name: GRB210813A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30640
SUBJECT: GRB 210813A: Fermi GBM Final Real-time Localization
DATE:    21/08/13 01:05:38 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 00:54:23 UT on 13 Aug 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210813A (trigger 650508868.674406 / 210813038).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 15.0, Dec = 8.1 (J2000 degrees, equivalent to J2000 01h 00m, 8d 05'), with a statistical uncertainty of 1.3 degrees.

The angle from the Fermi LAT boresight is 17.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210813038/quicklook/glg_skymap_all_bn210813038.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/bn210813038/quicklook/glg_healpix_all_bn210813038.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210813038/quicklook/glg_lc_medres34_bn210813038.gif


GRB_name: GRB210813A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30641
SUBJECT: Fermi GRB 210813A: Global MASTER-Net observations report 
DATE:    21/08/13 02:15:19 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-Tavrida robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 210813A ( Fermi GBM team, GCN 30640) errorbox  574 sec after notice time and 629 sec after trigger time at 2021-08-13 01:04:52 UT, with upper limit up to  16.5 mag. Observations started at twilight.  The observations began at zenith distance = 36 deg. The sun  altitude  is -16.1 deg. 

MASTER-IAC robotic telescope  located in Spain (IAC Teide Observatory) started inspect of the Fermi GRB 210813A errorbox  616 sec after notice time and 671 sec after trigger time at 2021-08-13 01:05:35 UT, with upper limit up to  19.8 mag. The observations began at zenith distance = 54 deg. The sun  altitude  is -47.3 deg. 

MASTER-Kislovodsk robotic telescope  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 210813A errorbox  626 sec after notice time and 681 sec after trigger time at 2021-08-13 01:05:44 UT, with upper limit up to  17.0 mag. Observations started at twilight.  The observations began at zenith distance = 35 deg. The sun  altitude  is -11.9 deg. 

The galactic latitude b = -54 deg., longitude l = 128 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1688882

We obtain a following upper limits.  

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

     694 | 2021-08-13 01:04:52 |      MASTER-Tavrida | (00h 56m 40.50s , +08d 15m 20.7s) |  P\ |   130 | 16.1 |        
     737 | 2021-08-13 01:05:35 |          MASTER-IAC | (00h 59m 18.91s , +07d 58m 47.0s) |  P| |   130 | 18.6 |        
     907 | 2021-08-13 01:05:35 |          MASTER-IAC | (00h 59m 18.91s , +07d 58m 47.0s) |  P| |   470 | 19.7 |  Coadd 
     737 | 2021-08-13 01:05:35 |          MASTER-IAC | (00h 58m 31.40s , +08d 03m 43.9s) |  P- |   130 | 18.4 |        
     907 | 2021-08-13 01:05:35 |          MASTER-IAC | (00h 58m 31.40s , +08d 03m 44.0s) |  P- |   470 | 19.3 |  Coadd 
     746 | 2021-08-13 01:05:44 |   MASTER-Kislovodsk | (01h 00m 05.80s , +08d 08m 53.0s) |  P- |   130 | 15.9 |        
     916 | 2021-08-13 01:05:44 |   MASTER-Kislovodsk | (01h 00m 05.81s , +08d 08m 53.0s) |  P- |   470 | 16.7 |  Coadd 
     746 | 2021-08-13 01:05:44 |   MASTER-Kislovodsk | (01h 00m 01.56s , +08d 32m 50.9s) |  P| |   130 | 16.5 |        
     916 | 2021-08-13 01:05:44 |   MASTER-Kislovodsk | (01h 00m 01.56s , +08d 32m 50.9s) |  P| |   470 | 17.0 |  Coadd 
     854 | 2021-08-13 01:07:22 |      MASTER-Tavrida | (00h 56m 48.35s , +08d 14m 14.6s) |  P\ |   150 | 16.1 |        
     902 | 2021-08-13 01:08:05 |          MASTER-IAC | (00h 59m 12.29s , +07d 57m 47.5s) |  P| |   160 | 18.9 |        
     902 | 2021-08-13 01:08:05 |          MASTER-IAC | (00h 58m 24.62s , +08d 02m 44.7s) |  P- |   160 | 18.7 |        
     911 | 2021-08-13 01:08:15 |   MASTER-Kislovodsk | (01h 00m 00.08s , +08d 07m 52.1s) |  P- |   160 | 16.3 |        
     912 | 2021-08-13 01:08:15 |   MASTER-Kislovodsk | (00h 59m 55.61s , +08d 31m 49.0s) |  P| |   160 | 16.5 |        
    1038 | 2021-08-13 01:10:11 |      MASTER-Tavrida | (00h 56m 40.82s , +08d 13m 07.9s) |  P\ |   180 | 16.3 |        
    1092 | 2021-08-13 01:11:05 |          MASTER-IAC | (00h 59m 18.07s , +07d 58m 13.7s) |  P| |   180 | 18.9 |        
    1092 | 2021-08-13 01:11:05 |          MASTER-IAC | (00h 58m 30.24s , +08d 03m 10.7s) |  P- |   180 | 18.6 |        
    1102 | 2021-08-13 01:11:15 |   MASTER-Kislovodsk | (01h 00m 01.28s , +08d 08m 52.3s) |  P- |   180 | 15.6 |        
    1102 | 2021-08-13 01:11:15 |   MASTER-Kislovodsk | (00h 59m 56.65s , +08d 32m 48.7s) |  P| |   180 | 15.9 |        
    1237 | 2021-08-13 01:13:30 |      MASTER-Tavrida | (00h 56m 47.22s , +08d 13m 07.5s) |  P\ |   180 | 16.3 |        
    1292 | 2021-08-13 01:14:25 |          MASTER-IAC | (00h 59m 16.05s , +07d 59m 28.3s) |  P| |   180 | 18.9 |        
    1472 | 2021-08-13 01:14:25 |          MASTER-IAC | (00h 59m 16.05s , +07d 59m 28.3s) |  P| |   540 | 19.8 |  Coadd 
    1292 | 2021-08-13 01:14:25 |          MASTER-IAC | (00h 58m 28.03s , +08d 04m 25.3s) |  P- |   180 | 18.7 |        
    1472 | 2021-08-13 01:14:25 |          MASTER-IAC | (00h 58m 28.03s , +08d 04m 25.3s) |  P- |   540 | 19.5 |  Coadd 
    1436 | 2021-08-13 01:16:49 |      MASTER-Tavrida | (00h 56m 43.91s , +08d 14m 33.0s) |  P\ |   180 | 16.5 |        
    1492 | 2021-08-13 01:17:45 |          MASTER-IAC | (00h 59m 16.03s , +07d 58m 00.8s) |  P| |   180 | 18.9 |        
    1492 | 2021-08-13 01:17:45 |          MASTER-IAC | (00h 58m 27.99s , +08d 02m 57.4s) |  P- |   180 | 18.7 |        
    1692 | 2021-08-13 01:21:05 |          MASTER-IAC | (00h 59m 19.72s , +07d 59m 27.8s) |  P| |   180 | 18.9 |        
    1692 | 2021-08-13 01:21:05 |          MASTER-IAC | (00h 58m 31.68s , +08d 04m 24.4s) |  P- |   180 | 18.7 |        
    1832 | 2021-08-13 01:24:25 |          MASTER-IAC | (01h 02m 54.77s , +07d 58m 50.4s) |   C |    60 | 18.6 |        
    1832 | 2021-08-13 01:24:25 |          MASTER-IAC | (00h 54m 47.04s , +08d 04m 10.4s) |   C |    60 | 18.5 |        
    2073 | 2021-08-13 01:28:26 |          MASTER-IAC | (01h 04m 28.98s , +08d 39m 17.4s) |   C |    60 | 18.6 |        
    2073 | 2021-08-13 01:28:26 |          MASTER-IAC | (00h 56m 20.95s , +08d 44m 37.3s) |   C |    60 | 18.5 |        
    2159 | 2021-08-13 01:29:53 |          MASTER-IAC | (01h 04m 18.57s , +06d 45m 19.4s) |   C |    60 | 18.8 |        
    2159 | 2021-08-13 01:29:53 |          MASTER-IAC | (00h 56m 12.85s , +06d 50m 38.5s) |   C |    60 | 18.6 |        
    2239 | 2021-08-13 01:31:12 |          MASTER-IAC | (01h 04m 54.89s , +10d 34m 56.1s) |   C |    60 | 18.9 |        
    2239 | 2021-08-13 01:31:12 |          MASTER-IAC | (00h 56m 44.12s , +10d 40m 16.4s) |   C |    60 | 18.6 |        
    2319 | 2021-08-13 01:32:32 |          MASTER-IAC | (00h 55m 57.65s , +04d 56m 56.9s) |   C |    60 | 18.6 |        
    2399 | 2021-08-13 01:33:52 |          MASTER-IAC | (01h 11m 51.00s , +08d 46m 45.3s) |   C |    60 | 18.5 |        
    2479 | 2021-08-13 01:35:12 |          MASTER-IAC | (01h 11m 25.54s , +06d 51m 45.4s) |   C |    60 | 18.6 |        
    3165 | 2021-08-13 01:46:38 |          MASTER-IAC | (01h 04m 35.83s , +08d 41m 07.8s) |   C |    60 | 18.9 |        
    3165 | 2021-08-13 01:46:38 |          MASTER-IAC | (00h 56m 28.07s , +08d 46m 27.5s) |   C |    60 | 18.6 |        
    3245 | 2021-08-13 01:47:58 |          MASTER-IAC | (01h 04m 12.26s , +06d 46m 13.0s) |   C |    60 | 18.8 |        
    3245 | 2021-08-13 01:47:58 |          MASTER-IAC | (00h 56m 06.81s , +06d 51m 31.9s) |   C |    60 | 18.6 |        
    3326 | 2021-08-13 01:49:19 |          MASTER-IAC | (01h 04m 51.02s , +10d 35m 16.0s) |   C |    60 | 18.8 |        
    3326 | 2021-08-13 01:49:19 |          MASTER-IAC | (00h 56m 40.51s , +10d 40m 36.5s) |   C |    60 | 18.7 |        
    3406 | 2021-08-13 01:50:39 |          MASTER-IAC | (00h 56m 00.81s , +04d 57m 29.8s) |   C |    60 | 18.6 |        
    3486 | 2021-08-13 01:51:59 |          MASTER-IAC | (01h 11m 44.33s , +08d 44m 44.5s) |   C |    60 | 18.5 |        
    3566 | 2021-08-13 01:53:19 |          MASTER-IAC | (01h 11m 30.53s , +06d 51m 06.1s) |   C |    60 | 18.7 |        
    4211 | 2021-08-13 02:04:04 |          MASTER-IAC | (01h 04m 28.84s , +08d 41m 11.7s) |   C |    60 | 18.9 |        
    4211 | 2021-08-13 02:04:04 |          MASTER-IAC | (00h 56m 20.65s , +08d 46m 31.4s) |   C |    60 | 18.7 |        
    4291 | 2021-08-13 02:05:24 |          MASTER-IAC | (01h 04m 17.37s , +06d 46m 10.2s) |   C |    60 | 18.7 |        
    4291 | 2021-08-13 02:05:24 |          MASTER-IAC | (00h 56m 11.51s , +06d 51m 29.7s) |   C |    60 | 18.6 |        
    4371 | 2021-08-13 02:06:44 |          MASTER-IAC | (01h 04m 51.49s , +10d 33m 12.8s) |   C |    60 | 18.9 |        
    4371 | 2021-08-13 02:06:44 |          MASTER-IAC | (00h 56m 40.56s , +10d 38m 33.5s) |   C |    60 | 18.8 |        
    4455 | 2021-08-13 02:08:09 |          MASTER-IAC | (00h 55m 58.70s , +04d 56m 38.8s) |   C |    60 | 18.6 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210813A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30642
SUBJECT: GRB 210813A: BALROG localization (Fermi Trigger 650508868 / GRB 210813038)
DATE:    21/08/13 04:08:35 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
650508868 at 00:54:23 on 13 Aug. 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) = 11.7+/-2.5 deg
Decl.(2000.0) = 8.6+/-2.2 deg
We estimate an additional systematic error of 1 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210813038/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210813038/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210813038/json

                        


GRB_name: GRB210712A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30643
SUBJECT: GRB 210712A: Fermi GBM observation
DATE:    21/08/13 07:31:38 GMT
FROM:    Elisabetta Bissaldi at INFN,Bari  <elisabetta.bissaldi@ba.infn.it>

E. Bissaldi (Politecnico and INFN Bari)
reports on behalf of the Fermi GBM Team:


"At 09:43:10.98 UT on 12 July 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210712A (trigger 647775795 / 210712405),
which was also detected by the Swift/BAT (Sbarufatti et al. 2021, GCN 30447).
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight
at the GBM trigger time is 36 degrees.

The GBM light curve consists of an emission episode
with a duration (T90) of about 8 s (50-300 keV).
The time-averaged spectrum from T0-0.3 s to T0+6.6 s is
adequately fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.04 +/- 0.13 and
the cutoff energy, parameterized as Epeak, is 230 +/- 50 keV.

The event fluence (10-1000 keV) in this time interval is
(1.51 +/- 0.17)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.1 s in the 10-1000 keV band
is 3.1 +/- 0.2 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: GRB210812A
Detection_method: INTEGRAL
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30645
SUBJECT: GRB 210812A is consistent with being a lensed GRB
DATE:    21/08/13 20:34:35 GMT
FROM:    Peter Veres at UAH  <veresp@gmail.com>

P. Veres (UAH) reports on behalf of the Fermi-GBM team:

"
Fermi GBM triggered on GRB 210812A at 16:47:01 UT on 12 Aug 2021 (trigger
650479626 / 210812699). Location information can be found in the Fermi GBM
team GCN 30633.

The lightcurve of GRB 210812A consists of two pulses, separated by about 33
s. The two pulses have similar shapes, the first pulse being approximately
5 times brighter.

The best fitting spectral shapes are consistent between the pulses. The
hardness ratio as a function of time also shows a consistent evolution.

These observations suggest that the two pulses are gravitationally lensed
manifestations of a single pulse.

Assuming a point mass lens model (e.g. Mao 1992, ApJL, 839, 41), the mass
of the lens is about 10^6 Msun.

GRB 210812A was also detected by INTEGRAL/SPI-ACS.

This analysis is preliminary, further analysis is ongoing. We encourage
follow-up observations.
"


GRB_name: GRB210815A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30647
SUBJECT: GRB 210815A: Fermi GBM Final Real-time Localization
DATE:    21/08/15 02:34:12 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 02:23:49 UT on 15 Aug 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210815A (trigger 650687034.634966 / 210815100).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 351.8, Dec = -30.2 (J2000 degrees, equivalent to J2000 23h 27m, -30d 11'), with a statistical uncertainty of 2.9 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/bn210815100/quicklook/glg_skymap_all_bn210815100.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/bn210815100/quicklook/glg_healpix_all_bn210815100.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210815100/quicklook/glg_lc_medres34_bn210815100.gif


GRB_name: GRB210815A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30648
SUBJECT: GRB 210815A: BALROG localization (Fermi Trigger 650687034 / GRB 210815100)
DATE:    21/08/15 07:49:08 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
650687034 at 02:23:49 on 15 Aug. 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) = 347.5+/-2.7 deg
Decl.(2000.0) = -39.9+/-2.7 deg
We estimate an additional systematic error of 1 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210815100/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210815100/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210815100/json

                        


GRB_name: GRB210818A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30652
SUBJECT: GRB 210818A: Swift detection of a burst with an optical counterpart
DATE:    21/08/18 01:26:40 GMT
FROM:    Kim Page at U.of Leicester  <klp5@leicester.ac.uk>

A. P. Beardmore (U Leicester), J. A. Kennea (PSU),
A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester) and
D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 01:02:08 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210818A (trigger=1069169).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 149.131, -87.031 which is 
   RA(J2000) = 09h 56m 32s
   Dec(J2000) = -87d 01' 52"
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 60 sec.  The peak count rate
was ~28000 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 01:03:06.9 UT, 59.0 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source with an enhanced position: RA, Dec 148.8666,
-87.0253 which is equivalent to:
   RA(J2000)  = 09h 55m 27.99s
   Dec(J2000) = -87d 01' 31.0"
with an uncertainty of 1.9 arcseconds (radius, 90% containment). This
location is 53 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 (1.74 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 4.7
(+2.38/-2.11) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 1.40e-08 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 66 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  = 09:55:28.15 = 148.86729
  DEC(J2000) = -87:01:28.8  = -87.02467
with a 90%-confidence error radius of about 0.62 arc sec. This position is 1.9
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.93 with a 1-sigma error of about  0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.213. 

Although this was originally reported in the GCN Notices as a known source
we believe that this is a GRB. 

Burst Advocate for this burst is A. P. Beardmore (apb AT star.le.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: GRB210818A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30653
SUBJECT: GRB 210818A: Enhanced Swift-XRT position
DATE:    21/08/18 05:20:55 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 1521 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 210818A, 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 = 148.86765, -87.02526 which is equivalent
to:

RA (J2000): 09h 55m 28.23s
Dec (J2000): -87d 01' 30.9"

with an uncertainty of 2.2 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: GRB210818A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30654
SUBJECT: GRB 210818A: AGILE detection
DATE:    21/08/18 08:27:40 GMT
FROM:    Alessandro Ursi at INAF/IAPS  <alessandro.ursi@gmail.com>

A. Ursi (INAF/IAPS), F. Verrecchia (SSDC, and INAF/OAR), C. Casentini
(INAF/IAPS), P. Tempesta (TeleSpazio), M. Tavani (INAF/IAPS, and Univ. Roma
Tor Vergata), A. Argan, M. Cardillo, Y. Evangelista, G. Piano (INAF/IAPS),
F. Lucarelli, C. Pittori,  (SSDC, and INAF/OAR), A. Bulgarelli, 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 210818A at T0 = 2021-08-18
01:02:08.19 s (UTC), reported by Swift (GCNs #30652, #30653).

The burst is clearly 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 about 35 s and
it released a total number of 3020 counts in the SA detector (above a
background rate of 70 Hz), 48170 counts in the MCAL detector (above a
background rate of 1250 Hz), and 130730 counts in the AC detector (above a
background rate of 3650 Hz). The AGILE ratemeter light curves can be found
at http://www.agilescienceapp.it/notices/GRB210818A_AGILE_RM.png .

The event also triggered a partial high time resolution MCAL data
acquisition, from T1 = 2021-08-18 01:02:07.81 s +/- 0.01 (UTC) to T2
=2021-08-18 01:02:21.18 +/- 0.01 s (UTC), and released 21640 counts in the
detector, above a background rate of 625 Hz. The MCAL light curve can be
found at:
http://www.agilescienceapp.it/notices/074408_GRB_556333328.188243.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: GRB210818A
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30655
SUBJECT: GRB 210818A: AstroSat CZTI detection
DATE:    21/08/18 12:01:28 GMT
FROM:    Gaurav Waratkar at IIT,Bombay  <gauravwaratkar@iitb.ac.in>

V. Prasad (IUCAA), P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute
(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 bright long GRB 210818A,
which was also detected by Swift-BAT (Beardmore et al., GCN #30652),
Swift-XRT (Osborne et al., GCN #30653) and AGILE (Ursi et al., GCN
#30654). 

The source was clearly detected in the 20-200 keV energy range, with the
strongest peak at 2021-08-18 01:02:10.5 UT in the single-peak light
curve. The measured peak count rate associated with the burst is 1018
(+64, -64) cts/s above the background in the combined data of four
quadrants, with a total of 13993 (+552, -512) cts. The local mean
background count rate was 526 (+3, -3) cts/s. Using cumulative rates, we
measure a T90 of 33 (+4, -3) s. 

It was also clearly detected in the CsI anticoincidence (Veto) detector
in the 100-500 keV energy range, with the strongest peak at 2021-08-18
01:02:09.9 UT in the single-peak light curve. The measured peak count
rate is 3748 (+116, -126) cts/s above the background in the combined
Veto data of four quadrants, with a total of 52829 (+844, -1097) cts.
The local mean background count rate was 1616 (+5, -5) cts/s. We measure
a T90 of 37 (+3, -2) 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 [1]. 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. 

Links:
------
[1] http://astrosat.iucaa.in/czti/?q=grb


GRB_name: GRB210818A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30657
SUBJECT: Konus-Wind detection of GRB 210818A
DATE:    21/08/18 18:23:06 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 210818A (Swift detection: Beardmore et al., GCN 30652;
AGILE detection: Ursi et al., GCN 30654)
triggered Konus-Wind (KW) at T0=3729.710 s UT (01:02:09.710).

The burst light curve started at ~T0 with a bright, short (<0.5s),
hard-spectrum initial pulse, which was followed, after a ~0.5 s interval,
by a similarly bright and hard, multi-peaked emission, which gradually decays until ~T0+90 s.
We also note a QPO-like behavior of the light curve in the interval
from ~T0+1.6 s to ~T0+3.2 s, with the quasi period of ~0.21 s.

The emission is seen up to ~7 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210818_T03729/

As observed by Konus-Wind, the burst had
a fluence of (2.67 Â± 0.12)x10^-4 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 0.128 s,
of (5.12 Â± 0.54)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst (measured from T0 to T0+80.640 s)
is best fit in the 20 keV - 20 MeV range
by a power law with exponential cutoff (CPL) model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.99(-0.03,+0.03) and Ep = 1107(-71,+78) keV (chi2 = 117/98 dof).
Fitting this spectrum by a Band function yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -3.2 (chi2 = 117/97 dof).

The spectrum near the peak count rate (measured from T0 to T0+0.256 s,
that corresponds to the short initial pulse)
is best fit in the 20 keV - 20 MeV range by the CPL model
with alpha = -0.28(-0.13,+0.14) and Ep = 1247(-133,+47) keV (chi2 = 38/58 dof).
Fitting this spectrum by a Band function yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -3.4 (chi2 = 38/57 dof).

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


GRB_name: GRB210726A
Detection_method: VLA Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30658
SUBJECT: GRB 210726A: VLA radio afterglow detection
DATE:    21/08/18 20:48:40 GMT
FROM:    Genevieve Schroeder at Northwestern University  <genevieveschroeder2023@u.northwestern.edu>

G. Schroeder, K. D. Alexander, W. Fong, A. Rouco Escorial, (Northwestern),
T. Laskar (U. of Bath), E. Berger (Harvard) report:

"We re-observed the position of short GRB 210726A (Bernardini et al., GCN
30523; Veres et al., GCN 30540; Palmer et al., GCN 30536; Tohuvavohu et
al., GCN 30535) with the Karl G. Jansky Very Large Array (VLA) under
program 20B-057 (PI: Fong) beginning on 2021 August 07.02 UT (11.21 days
post-burst) at a mean frequency of 6 GHz.

In 1.5 hour of observations we detect a radio source with a preliminary
flux density of ~40 uJy. The position of this radio source is fully
consistent with the position of the X-ray afterglow (Osborne et al., GCN
30524; Rouco Escorial et al., GCN 30558) at:

RA(J2000): 12:53:09.8

Dec(J2000): +19:11:25.1

with an uncertainty of 0.6 arcsec in each coordinate.

We obtained further VLA observations at 6 GHz and 10 GHz beginning on 2021
August 14.75 UT (18.94 days post-burst) and detect the source at both
frequencies. We find a significant brightening at 6 GHz, confirming this
source as the radio afterglow of GRB210726A. We note that this radio
afterglow is among the brightest ever detected for a short GRB to date.

Further observations are planned. We thank the VLA staff for quickly
approving and executing these observations."


GRB_name: GRB210818A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30659
SUBJECT: GRB 210818A: Swift-BAT refined analysis
DATE:    21/08/18 21:36:00 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

H. A. Krimm (NSF), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), S. Laha (GSFC/UMBC),
A. Y. Lien (U Tampa), 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-240 to T+962 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 210818A (trigger #1069169)
(Beardmore et al., GCN Circ. 30652).  The BAT ground-calculated position is
RA, Dec = 148.949, -87.029 deg which is
   RA(J2000)  =  09h 55m 47.7s
   Dec(J2000) = -87d 01' 45.3"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 97%.

The mask-weighted light curve shows many overlapping pulses on top of
a general FRED-like structure. The burst emission starts at ~T0, peaks
at ~T+2 s, and ends at ~T+130 s. T90 (15-350 keV) is 73.56 +- 1.55 sec
(estimated error including systematics).

The time-averaged spectrum from T-0.69 to T+128.97 sec is best fit
by a simple power-law model.  The power law index of the time-averaged
spectrum is 1.22 +- 0.03.  The fluence in the 15-150 keV band is
2.6 +- 0.03 x 10^-5 erg/cm2. The 1-sec peak photon flux measured from
T+1.20 sec in the 15-150 keV band is 11.2 +- 0.4 ph/cm2/sec.
All the quoted errors are at the 90% confidence level.


GRB_name: GRB210818A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30660
SUBJECT: GRB 210818A: Swift-XRT refined Analysis
DATE:    21/08/18 22:39:25 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),
J. D. Gropp (PSU), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), K.L.
Page (U. Leicester) and A.P. Beardmore report on behalf of the
Swift-XRT team:

We have analysed 7.1 ks of XRT data for GRB 210818A (Beardmore et al.
GCN Circ. 30652), from 65 s to 69.5 ks after the  BAT trigger. The data
comprise 188 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. 30653).

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=1.04 (+/-0.20). At T+111 s  the decay
steepens to an alpha of 6.8 (+0.7, -0.6). The light curve breaks again
at T+157 s to a decay with alpha=0.67 (+0.38, -0.29),  before a final
break at T+479 s s after which the decay index is 1.50 (+/-0.06).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 0.86 (+/-0.06). The
best-fitting absorption column is  2.5 (+0.5, -0.4) x 10^21 cm^-2, in
excess of the Galactic value of 1.7 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.64 (+0.14, -0.11)
and a best-fitting absorption column of 1.94 (+0.56, -0.20) x 10^21
cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 4.4 x 10^-11 (5.3 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.94 (+0.56, -0.20) x 10^21 cm^-2
Galactic foreground: 1.7 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.64 (+0.14, -0.11)

If the light curve continues to decay with a power-law decay index of
1.50, the count rate at T+24 hours will be 3.1 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.3 x
10^-13 (1.6 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/01069169.

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


GRB_name: GRB210818A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30661
SUBJECT: Swift GRB 210818A: Global MASTER-Net observations report 
DATE:    21/08/19 01:06:55 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 210818A ( A. P. Beardmore et al., GCN 30652) errorbox  22995 sec after notice time and 23077 sec after trigger time at 2021-08-18 07:27:44 UT, with upper limit up to  18.9 mag. The observations began at zenith distance = 62 deg. The sun  altitude  is -47.3 deg. 

The galactic latitude b = -25 deg., longitude l = 301 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1693376

We obtain a following upper limits.  

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

   23167 |         MASTER-OAFA |   C |   180 | 13.8 |        
   23347 |         MASTER-OAFA |   C |   540 | 14.9 |  Coadd 
   23379 |         MASTER-OAFA |   C |   180 | 14.9 |        
   23559 |         MASTER-OAFA |   C |   540 | 15.3 |  Coadd 
   23592 |         MASTER-OAFA |   C |   180 | 14.6 |        
   23812 |         MASTER-OAFA |   C |   180 | 14.3 |        
   24026 |         MASTER-OAFA |   C |   180 | 14.8 |        
   24242 |         MASTER-OAFA |   C |   180 | 15.8 |        
   24456 |         MASTER-OAFA |   C |   180 | 15.0 |        
   24636 |         MASTER-OAFA |   C |   540 | 17.0 |  Coadd 
   24668 |         MASTER-OAFA |   C |   180 | 14.9 |        
   24883 |         MASTER-OAFA |   C |   180 | 16.4 |        
   25099 |         MASTER-OAFA |   C |   180 | 17.3 |        
   25279 |         MASTER-OAFA |   C |   540 | 18.0 |  Coadd 
   25329 |         MASTER-OAFA |   C |   180 | 17.4 |        
   25546 |         MASTER-OAFA |   C |   180 | 17.4 |        
   25762 |         MASTER-OAFA |   C |   180 | 16.9 |        
   25942 |         MASTER-OAFA |   C |   540 | 18.0 |  Coadd 
   25975 |         MASTER-OAFA |   C |   180 | 18.0 |        
   26190 |         MASTER-OAFA |   C |   180 | 17.3 |        
   26405 |         MASTER-OAFA |   C |   180 | 17.3 |        
   26585 |         MASTER-OAFA |   C |   540 | 17.6 |  Coadd 
   26621 |         MASTER-OAFA |   C |   180 | 17.7 |        
   26833 |         MASTER-OAFA |   C |   180 | 17.5 |        
   27049 |         MASTER-OAFA |   C |   180 | 17.7 |        
   27229 |         MASTER-OAFA |   C |   540 | 18.3 |  Coadd 
   27264 |         MASTER-OAFA |   C |   180 | 17.5 |        
   27479 |         MASTER-OAFA |   C |   180 | 17.7 |        
   27691 |         MASTER-OAFA |   C |   180 | 17.5 |        
   27871 |         MASTER-OAFA |   C |   540 | 18.5 |  Coadd 
   27906 |         MASTER-OAFA |   C |   180 | 17.6 |        
   28123 |         MASTER-OAFA |   C |   180 | 18.2 |        
   28337 |         MASTER-OAFA |   C |   180 | 17.7 |        
   28517 |         MASTER-OAFA |   C |   540 | 18.1 |  Coadd 
   28551 |         MASTER-OAFA |   C |   180 | 17.3 |        
   28765 |         MASTER-OAFA |   C |   180 | 18.0 |        
   28983 |         MASTER-OAFA |   C |   180 | 18.0 |        
   29199 |         MASTER-OAFA |   C |   180 | 17.9 |        
   29415 |         MASTER-OAFA |   C |   180 | 17.7 |        
   29595 |         MASTER-OAFA |   C |   540 | 18.0 |  Coadd 
   29630 |         MASTER-OAFA |   C |   180 | 17.5 |        
   29810 |         MASTER-OAFA |   C |   540 | 18.6 |  Coadd 
   29842 |         MASTER-OAFA |   C |   180 | 18.2 |        
   30058 |         MASTER-OAFA |   C |   180 | 18.4 |        
   30272 |         MASTER-OAFA |   C |   180 | 18.2 |        
   30488 |         MASTER-OAFA |   C |   180 | 17.8 |        
   30701 |         MASTER-OAFA |   C |   180 | 18.0 |        
   30881 |         MASTER-OAFA |   C |   540 | 18.9 |  Coadd 
   30917 |         MASTER-OAFA |   C |   180 | 18.1 |        
   31130 |         MASTER-OAFA |   C |   180 | 18.3 |        
   31329 |         MASTER-OAFA |   C |   180 | 18.3 |        
   31729 |         MASTER-OAFA |   C |   180 | 18.4 |        
   31909 |         MASTER-OAFA |   C |   540 | 18.5 |  Coadd 
   31928 |         MASTER-OAFA |   C |   180 | 18.4 |        
   32127 |         MASTER-OAFA |   C |   180 | 18.0 |        
   32327 |         MASTER-OAFA |   C |   180 | 17.4 |        
   32507 |         MASTER-OAFA |   C |   540 | 18.0 |  Coadd 
   32527 |         MASTER-OAFA |   C |   180 | 17.3 |        
   32726 |         MASTER-OAFA |   C |   180 | 17.1 |        
   32926 |         MASTER-OAFA |   C |   180 | 17.3 |        
   33106 |         MASTER-OAFA |   C |   540 | 17.9 |  Coadd 
   33125 |         MASTER-OAFA |   C |   180 | 17.5 |        
   33325 |         MASTER-OAFA |   C |   180 | 17.1 |        
   33524 |         MASTER-OAFA |   C |   180 | 16.7 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210820A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30664
SUBJECT: GRB 210820A: Swift detection of a burst with an optical counterpart
DATE:    21/08/20 17:52:12 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

A. P. Beardmore (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU),
N. J. Klingler (GSFC/UMBC/CRESSTII), N. P. M. Kuin (UCL-MSSL),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),
D. M. Palmer (LANL) and A. Tohuvavohu (U Toronto) report on behalf of
the Neil Gehrels Swift Observatory Team:

At 17:38:00 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210820A (trigger=1069551).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 20.629, +4.632 which is 
   RA(J2000) = 01h 22m 31s
   Dec(J2000) = +04d 37' 55"
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 30 sec.  The peak count rate
was ~500 counts/sec (15-350 keV), at ~8 sec after the trigger. 

The XRT began observing the field at 17:40:05.7 UT, 125.0 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 20.6376, 4.6071 which is equivalent to:
   RA(J2000)  = 01h 22m 33.02s
   Dec(J2000) = +04d 36' 25.6"
with an uncertainty of 11.1 arcseconds (radius, 90% containment). This
location is 94 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy. 

The initial flux in the 2.5 s image was 3.75e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 250 seconds with the U filter starting
130 seconds after the BAT trigger. There is a candidate afterglow in the
rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  = 01:22:33.48 =  20.63952
  DEC(J2000) = +04:36:28.2  = 4.60783
with a 90%-confidence error radius of about 0.76 arc sec. This position is 7.4
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.53 with a 1-sigma error of about  0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.031. 

Burst Advocate for this burst is A. P. Beardmore (apb AT star.le.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: GRB210820B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30665
SUBJECT: GRB 210820B: Fermi GBM Final Localization
DATE:    21/08/20 18:26:00 GMT
FROM:    Joshua Wood at MSFC/Fermi-GBM  <joshua.r.wood@nasa.gov>

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

At 00:05:14.01 UT on 20 Aug 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210820B (trigger 651110719 / 210820004).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 277.0, Dec = +67.0 (J2000 degrees, equivalent to J2000 18h 28m, +67d 00'), with a statistical uncertainty of 5.0 degrees.

The angle from the Fermi LAT boresight is 31.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210820004/quicklook/glg_skymap_all_bn210820004.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/bn210820004/quicklook/glg_healpix_all_bn210820004.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210820004/quicklook/glg_lc_medres34_bn210820004.gif


GRB_name: GRB210820A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30666
SUBJECT: Swift GRB 210820A: Global MASTER-Net observations report 
DATE:    21/08/20 19:03:39 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) was pointed to the Swift GRB 210820A ( A. P. Beardmore et al., GCN 30664) errorbox  4451 sec after notice time and 4532 sec after trigger time at 2021-08-20 18:53:33 UT, with upper limit up to  15.2 mag. The observations began at zenith distance = 84 deg. The sun  altitude  is -26.1 deg. 

The galactic latitude b = -57 deg., longitude l = 138 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1695760

We obtain a following upper limits.  

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

    4622 |   MASTER-Kislovodsk |   C |   180 | 14.5 |        
    4622 |   MASTER-Kislovodsk |   C |   180 | 15.2 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210820A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30667
SUBJECT: GRB 210820A: Enhanced Swift-XRT position
DATE:    21/08/21 02:29:36 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 2824 s of XRT Photon Counting mode data and 3 UVOT
images for GRB 210820A, 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 = 20.63963, +4.60764 which is equivalent
to:

RA (J2000): 01h 22m 33.51s
Dec (J2000): +04d 36' 27.5"

with an uncertainty of 2.5 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: GRB210820A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30668
SUBJECT: GRB 210820A: Swift-XRT refined Analysis
DATE:    21/08/21 02:38:02 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.A. Kennea (PSU), A.
Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), K.L. Page (U. Leicester)
and A.P. Beardmore report on behalf of the Swift-XRT team:

We have analysed 6.5 ks of XRT data for GRB 210820A (Beardmore et al.
GCN Circ. 30664), from 131 s to 18.2 ks after the  BAT trigger. The
data comprise 339 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Beardmore et al. (GCN Circ. 30667).

The late-time light curve (from T0+5.9 ks) can be modelled with a
power-law decay with a decay index of alpha=1.9 (+0.6, -0.5).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.77 (+/-0.03). The
best-fitting absorption column is  1.20 (+/-0.11) x 10^21 cm^-2, in
excess of the Galactic value of 3.6 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.28 (+0.25, -0.13)
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 2.9 x 10^-11 (3.3 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      3.6 (+4.3, -0.0) x 10^20 cm^-2
Galactic foreground: 3.6 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:      2.28 (+0.25, -0.13)

If the light curve continues to decay with a power-law decay index of
1.9, the count rate at T+24 hours will be 2.9 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.4 x
10^-15 (9.6 x 10^-15) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01069551.

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


GRB_name: GRB210820A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30669
SUBJECT: GRB 210820A: Nanshan/NEXT optical upper limit
DATE:    21/08/21 04:01:10 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 210820A (Beardmore et al., GCN 30664) using 
the NEXT-0.6m telescope located at Nanshan, Xinjiang, China. We obtained 
10x200 s frames in the Sloan r-band, starting at 21:17:58 UT on 
2021-08-20, i.e., 3.67 hr after the BAT trigger.

No optical source is detected in our stacked image at the Swift/UVOT 
position (Beardmore et al., GCN 30664), down to a limiting magnitude of 
r~21.3, calibrated with the nearby PanSTARRS field.


GRB_name: GRB210820A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30670
SUBJECT: GRB 210820A: NOT optical upper limit
DATE:    21/08/21 07:30:12 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

Z.P. Zhu (NAOC, HUST), D. B. Malesani (DTU space), L. Izzo (DARK/NBI), 
J.P.U. Fynbo (DAWN/NBI), D. Xu (NAOC), R. Clavero (NOT) report on behalf 
of a larger collaboration:

We observed the field of GRB210820A (Beardmore et al., GCN30664) using 
the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. We 
obtained 3x200s frames in the Sloan r- filter, starting at 00:49:56 UT 
on 2021-08-21 (i.e., ~ 7.29 hr after the BAT trigger).

No optical source is detected in our stacked image at the Swift/UVOT 
position (Beardmore et al., GCN 30664), down to a limiting magnitude of 
r~22.2, calibrated with the nearby PanSTARRS field.


GRB_name: GRB210821A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30671
SUBJECT: GRB 210821A: Fermi GBM Final Real-time Localization
DATE:    21/08/21 07:51:40 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 07:40:28 UT on 21 Aug 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210821A (trigger 651224433.594692 / 210821320).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 49.3, Dec = -6.9 (J2000 degrees, equivalent to J2000 03h 17m, -6d 54'), with a statistical uncertainty of 2.0 degrees.

The angle from the Fermi LAT boresight is 87.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210821320/quicklook/glg_skymap_all_bn210821320.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/bn210821320/quicklook/glg_healpix_all_bn210821320.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210821320/quicklook/glg_lc_medres34_bn210821320.gif


GRB_name: GRB210820A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30672
SUBJECT: GRB 210820A: RATIR Optical Detections
DATE:    21/08/21 15:52:28 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), Eleonora Troja (GSFC), Michael G. Richer (UNAM), Ori Fox
(STScI),
J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Enrico Ramirez-Ruiz (UCSC),
JesÃºs GonzÃ¡lez (UNAM), Carlos RomÃ¡n-ZÃºÃ±iga (UNAM), Harvey Moseley (GSFC),
Rosa
L. Becerra (UNAM), Simone Dichiara (UMD), and OcÃ©lotl LÃ³pez (UNAM) report:

We observed the field of GRB 210820A (Beardmore, et al., GCN 30664) 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 2021/08 21.27 to 2021/08 21.50 UTC (12.47 to 17.96
hours after the BAT trigger), obtaining a total of 3.70 hours exposure
in the r and i bands.

We detect one source within the Swift-XRT error circle (Beardmore, et al.,
GCN 30667).  In comparison with the SDSS DR9 and 2MASS catalogs, we obtain:

  r = 22.84 +/- 0.22
  i = 22.66 +/- 0.18

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.

The source is located at RA, Dec = 1:22:33.47, +4:36:28.1 (J2000, +/-0.5").
This is 0.2 arcsec away from the UVOT OT (GCN 30664).

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


GRB_name: GRB210820A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30673
SUBJECT: GRB 210820A: LCO Optical Upper Limit
DATE:    21/08/21 16:05:02 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 210820A (Beardmore, et al., GCN 30664) with the LCO 1-m Sinistro instrument at the Teide Observatory, Tenerife site, on August 21, from 01:20 to 01:51 UT (corresponding to 7.7 to 8.5 hours from the GRB trigger time) with the Bessel R and I filters.

We performed a series of 5x120s exposures in R and I. In the UVOT detection region (Beardmore, et al., GCN 30664) no optical counterpart could be detected down to the following upper limits, calculated using the USNO-B.1 catalog as reference:

R>20.16

I>19.17

These magnitudes are not corrected for galactic extinction.

R.S. is funded by NSF AST grant #1831682


GRB_name: GRB210820A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30674
SUBJECT: GRB 210820A: LT optical upper limit
DATE:    21/08/21 17:30:40 GMT
FROM:    Martin Blazek at HETH/IAA-CSIC  <alf@iaa.es>

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

We observed the location of the Swift GRB 210820A (Beardmore et al., GCN
#30664) with 2-m Liverpool Telescope located in La Palma, Canary Isands,
Spain. We obtained 15 x 60 s images beginning 2021-08-21 03:29:30 UT. In
a stack of all images, centered at 0.4175 days after the GRB, no source is
detected at the UVOT position. Measured against three nearby SDSS stars, we
derive an upper limit of r' > 21.1 mag. This agrees with the non-detections
reported by Lipunov et al. (GCN #30666), Fu et al. (GCN #30669)., and Zhu et
al. (GCN #30670).


GRB_name: GRB210820A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30675
SUBJECT: GRB 210820A: Swift-BAT refined analysis
DATE:    21/08/21 18:36:42 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester),  H. A. Krimm (NSF),
A. Y. Lien (U Tampa), 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 210820A (trigger #1069551)
(Beardmore et al., GCN Circ. 30664).  The BAT ground-calculated position is
RA, Dec = 20.622, 4.642 deg which is
   RA(J2000)  =  01h 22m 29.4s
   Dec(J2000) = +04d 38' 30.6"
with an uncertainty of 3.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 48%.

The mask-weighted light curve shows many weak overlapping pulses
that start at ~T0 and end at ~T+260 s. T90 (15-350 keV) is
196.8 +- 51.4 sec (estimated error including systematics).

The time-averaged spectrum from T+0.78 to T+258.97 sec is best fit by
a simple power-law model.  The power law index of the time-averaged
spectrum is 2.26 +- 0.22.  The fluence in the 15-150 keV band is
1.5 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from
T+10.92 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/1069551/BA/


GRB_name: GRB210821A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30676
SUBJECT: Fermi GRB 210821A: Global MASTER-Net observations report 
DATE:    21/08/21 23:19:57 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 210821A ( Fermi GBM team, GCN 30671) errorbox  50201 sec after notice time and 50230 sec after trigger time at 2021-08-21 21:37:39 UT, with upper limit up to  12.6 mag. The observations began at zenith distance = 80 deg. The sun  altitude  is -34.8 deg. 

MASTER-Tavrida robotic telescope  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 210821A errorbox  54267 sec after notice time and 54295 sec after trigger time at 2021-08-21 22:45:24 UT, with upper limit up to  16.8 mag. The observations began at zenith distance = 76 deg. The sun  altitude  is -32.5 deg. 

The galactic latitude b = -49 deg., longitude l = 190 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1696282

We obtain a following upper limits.  

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

   50261 | 2021-08-21 21:37:39 |   MASTER-Kislovodsk | (03h 06m 09.35s , -06d 43m 00.6s) |   C |    60 | 12.0 |        
   50421 | 2021-08-21 21:40:19 |   MASTER-Kislovodsk | (03h 05m 37.89s , -04d 47m 03.2s) |   C |    60 | 12.6 |        
   50742 | 2021-08-21 21:45:40 |   MASTER-Kislovodsk | (03h 06m 55.76s , -08d 34m 58.7s) |   C |    60 | 12.6 |        
   54326 | 2021-08-21 22:45:24 |      MASTER-Tavrida | (03h 20m 05.86s , -06d 10m 34.8s) |   C |    60 | 16.2 |        
   54815 | 2021-08-21 22:53:33 |      MASTER-Tavrida | (03h 12m 55.02s , -08d 06m 16.1s) |   C |    60 | 16.3 |        
   55229 | 2021-08-21 23:00:27 |      MASTER-Tavrida | (03h 21m 00.76s , -08d 04m 15.3s) |   C |    60 | 16.3 |        
   55410 | 2021-08-21 23:03:28 |      MASTER-Tavrida | (03h 12m 06.09s , -06d 12m 19.0s) |   C |    60 | 16.8 |        
   55661 | 2021-08-21 23:07:39 |      MASTER-Tavrida | (03h 20m 05.24s , -06d 10m 15.9s) |   C |    60 | 16.6 |        
   56075 | 2021-08-21 23:14:33 |      MASTER-Tavrida | (03h 12m 54.77s , -08d 04m 12.7s) |   C |    60 | 16.8 |        
   56154 | 2021-08-21 23:15:52 |      MASTER-Tavrida | (03h 21m 06.28s , -08d 05m 06.5s) |   C |    60 | 16.5 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210822A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30677
SUBJECT: GRB 210822A: Swift detection of a burst with an optical afterglow
DATE:    21/08/22 09:52:13 GMT
FROM:    Kim Page at U.of Leicester  <klp5@leicester.ac.uk>

K. L. Page (U Leicester), J.D. Gropp (PSU), N. P. M. Kuin (UCL-MSSL)
and A. Y. Lien (U Tampa) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 09:18:18 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210822A (trigger=1069788).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 304.476, +5.265 which is 
   RA(J2000) = 20h 17m 54s
   Dec(J2000) = +05d 15' 54"
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 30 sec.  The peak count rate
was ~38000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 09:19:32.7 UT, 74.6 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 304.4377, 5.2786 which is equivalent to:
   RA(J2000)  = 20h 17m 45.05s
   Dec(J2000) = +05d 16' 43.0"
with an uncertainty of 11.9 arcseconds (radius, 90% containment). This
location is 145 arcseconds from the BAT onboard position, within the
BAT error circle. No event data are yet available to determine the
column density using X-ray spectroscopy. 

The initial flux in the 0.1 s image was 1.25e-08 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 250 seconds with the U filter  
starting 297 seconds after the BAT trigger. An afterglow   candidate
has been found in the initial data products with a magnitude 
 of u = 13.81 +/- 0.03. No correction  has been made for the expected 
extinction corresponding to E(B-V) of  0.162.   The preliminary UVOT 
position is RA=304.43748, Dec = 5.28337 (J2000),  which is equivalent 
to:   
   RA = 20h 17m 45.0s,  
   Dec = +05d 17m 00.1s (J2000)    with an  uncertainty of about an
arcsecond. 

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: GRB210822A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30678
SUBJECT: GRB 210822A: GECAM detection
DATE:    21/08/22 11:31:19 GMT
FROM:    Shaolin Xiong at IHEP  <xiongsl@ihep.ac.cn>

C. W. Wang, S. L. Xiong, X. Y. Zhao, X. Y. Song, C. Cai, C. Y. Li,
Y. Huang, S. L. Xie, J. C. Liu, Y. Q. Zhang,  Y. Zhao, Z. W. Guo, C. Zheng,
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, G. X. Sun, X. L. Sun, Y. L. Tuo, J. Z. Wang,X. L. Zhang,
W. C. Xue, X. Y. Wen, S. Xiao, 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. Wang, 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 in-flight
by a long bright burst, GRB 210822A, at 2021-08-22T09:18:18.00 UTC
(denoted as T0), which is also observed by Swift/BAT (GCN #30677).
Its alert data was downlinked to the ground through the
short message service of BeiDou Navigation Satellite System (BDS).

According to the GECAM-B light curves in about 30-1000 keV
from BDS alert data, this burst mainly consists of multiple
pulses with a duration of about 15 s.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_lc_grd_all_combine_83323099.png

An automatic localization was calculated using the light curves and 
spectrum,
and the GECAM location is consistent with the Swift/BAT position within 
the error.

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: GRB210822A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30679
SUBJECT: GRB 210822A: KAIT Optical Afterglow Confirmation
DATE:    21/08/22 15:25:27 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 210822A (Page et al.,

GCN 30677; see also GECAM detection, Wang et al., GCN 30678)

starting at 09:20:02 UT, 104s after the burst.

Observations were performed with a sequence in the clear (roughly R),

V, and I filters, and the exposure time was 20 s per image.

The bright optical afterglow reported by UVOT (Page et al., GCN 30677)

was clearly detected in our single image. We measure its brightness

of 11.4 mag in our first clear image at 114s after the burst, then

decayed to 16.1 mag at 2690s after the burst.

A preliminary KAIT clear band light curve is available at:


https://w.astro.berkeley.edu/~zwk/grb/GRB210822A/GRB210822A_kait.png


GRB_name: GRB210822A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30680
SUBJECT: GRB 210822A: RATIR Optical Detections
DATE:    21/08/22 16:59:44 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), Eleonora Troja (GSFC), Michael G. Richer (UNAM), Ori Fox
(STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Enrico Ramirez-Ruiz
(UCSC), JesÃºs GonzÃ¡lez (UNAM), Carlos RomÃ¡n-ZÃºÃ±iga (UNAM), Harvey Moseley
(GSFC), Rosa L. Becerra (UNAM), Simone Dichiara (UMD), and OcÃ©lotl LÃ³pez
(UNAM) report:

We observed the field of GRB 210822A (Page, et al., GCN 30677) 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 2021/08 22.39 to 2021/08 22.41 UTC (1.2 minutes to 0.49
hours after the BAT trigger), obtaining a total of 0.19 hours exposure in
the r and i bands.

We detect the fading OT (see, Zheng & Filippenko, GCN 30679) with high
confidence.   The flux varies approximately as t^(-1) from i = 13.2 to i =
15.8 (and r=15.6).  These preliminary 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: GRB210822A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30681
SUBJECT: Swift GRB 210822A: Global MASTER-Net observations report 
DATE:    21/08/22 17:07:28 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) was pointed to the Swift GRB 210822A ( K. L. Page et al., GCN 30677) errorbox  27300 sec after notice time and 27365 sec after trigger time at 2021-08-22 16:54:24 UT, with upper limit up to  16.2 mag. Observations started at twilight.  The observations began at zenith distance = 68 deg. The sun  altitude  is -8.8 deg. 

The galactic latitude b = -17 deg., longitude l = 48 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1697012

We obtain a following upper limits.  

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

   27456 |         MASTER-SAAO |   C |   180 | 16.2 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210822A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30682
SUBJECT: GRB 210822A: Enhanced Swift-XRT position
DATE:    21/08/22 17:08:09 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 501 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 210822A, 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 = 304.43756, +5.28349 which is equivalent
to:

RA (J2000): 20h 17m 45.01s
Dec (J2000): +05d 17' 00.6"

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: GRB210822B
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30683
SUBJECT: GRB 210822B: Fermi GBM Final Real-time Localization
DATE:    21/08/22 17:40:48 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 17:30:24 UT on 22 Aug 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210822B (trigger 651346229.489012 / 210822729).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 238.2, Dec = 18.0 (J2000 degrees, equivalent to J2000 15h 52m, 18d 00'), with a statistical uncertainty of 4.8 degrees.

The angle from the Fermi LAT boresight is 74.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210822729/quicklook/glg_skymap_all_bn210822729.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/bn210822729/quicklook/glg_healpix_all_bn210822729.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210822729/quicklook/glg_lc_medres34_bn210822729.gif


GRB_name: GRB210822A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30684
SUBJECT: GRB 210822A: Nanshan/NEXT optical observations
DATE:    21/08/22 18:35:26 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 210822A (Page et al., GCN 30677) using the 
NEXT-0.6m telescope located at Nanshan, Xinjiang, China. We obtained 
15x100 s frames in the Sloan r-band and 10x100 s frames in the V-band, 
starting at 14:42:53 UT on 2021-08-22, i.e., 5.41 hr after the BAT trigger.

The optical afterglow (e.g., Page et al., GCN 30677; Zheng & Filippenko, 
GCN 30679) of the burst is clearly detected in our stacked images. 
Preliminary photometry results are as follows:

    Tmid (UT)            Tmid-T0(day)  Mag   MagErr  Filter
2021-08-22T14:58:04    0.236      18.53    0.06      r
2021-08-22T15:54:29    0.275      18.88    0.08      V

calibrated with nearby PanSTARRS stars.


GRB_name: GRB210822B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30685
SUBJECT: Fermi GRB 210822B: Global MASTER-Net observations report 
DATE:    21/08/22 18:43:24 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-Tavrida robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 210822B ( Fermi GBM team, GCN 30683) errorbox  387 sec after notice time and 579 sec after trigger time at 2021-08-22 17:40:03 UT, with upper limit up to  18.6 mag. Observations started at twilight.  The observations began at zenith distance = 37 deg. The sun  altitude  is -11.4 deg. 

MASTER-SAAO robotic telescope  located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 210822B errorbox  2167 sec after notice time and 2359 sec after trigger time at 2021-08-22 18:09:43 UT, with upper limit up to  18.1 mag. The observations began at zenith distance = 58 deg. The sun  altitude  is -24.7 deg. 

The galactic latitude b = 47 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=1697277

We obtain a following upper limits.  

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

     639 | 2021-08-22 17:40:03 |      MASTER-Tavrida | (15h 53m 58.93s , +17d 53m 42.3s) |   C |   120 | 17.7 |        
     974 | 2021-08-22 17:46:08 |      MASTER-Tavrida | (15h 57m 41.09s , +18d 10m 19.7s) |   C |    60 | 18.4 |        
    1053 | 2021-08-22 17:47:27 |      MASTER-Tavrida | (16h 06m 01.45s , +18d 09m 19.4s) |   C |    60 | 18.6 |        
    1132 | 2021-08-22 17:48:46 |      MASTER-Tavrida | (15h 47m 45.39s , +16d 16m 38.2s) |   C |    60 | 18.0 |        
    1211 | 2021-08-22 17:50:05 |      MASTER-Tavrida | (15h 56m 05.66s , +16d 15m 23.9s) |   C |    60 | 18.2 |        
    1291 | 2021-08-22 17:51:25 |      MASTER-Tavrida | (15h 41m 33.74s , +18d 09m 58.1s) |   C |    60 | 18.0 |        
    1369 | 2021-08-22 17:52:43 |      MASTER-Tavrida | (15h 50m 00.13s , +18d 10m 59.7s) |   C |    60 | 18.0 |        
    1449 | 2021-08-22 17:54:03 |      MASTER-Tavrida | (15h 54m 50.24s , +14d 21m 55.7s) |   C |    60 | 18.3 |        
    1528 | 2021-08-22 17:55:22 |      MASTER-Tavrida | (16h 03m 00.47s , +14d 20m 56.1s) |   C |    60 | 18.3 |        
    1750 | 2021-08-22 17:59:04 |      MASTER-Tavrida | (16h 01m 05.04s , +20d 04m 55.6s) |   C |    60 | 18.6 |        
    2176 | 2021-08-22 18:06:10 |      MASTER-Tavrida | (16h 12m 01.08s , +16d 15m 34.5s) |   C |    60 | 18.0 |        
    2255 | 2021-08-22 18:07:29 |      MASTER-Tavrida | (15h 57m 35.96s , +18d 08m 27.0s) |   C |    60 | 18.4 |        
    2334 | 2021-08-22 18:08:48 |      MASTER-Tavrida | (16h 06m 07.95s , +18d 08m 42.7s) |   C |    60 | 18.5 |        
    2449 | 2021-08-22 18:09:43 |         MASTER-SAAO | (15h 52m 16.53s , +20d 02m 07.5s) |   C |   180 | 17.4 |        
    2413 | 2021-08-22 18:10:07 |      MASTER-Tavrida | (15h 47m 46.58s , +16d 15m 56.7s) |   C |    60 | 18.0 |        
    2492 | 2021-08-22 18:11:26 |      MASTER-Tavrida | (15h 56m 06.69s , +16d 14m 39.4s) |   C |    60 | 18.1 |        
    2571 | 2021-08-22 18:12:45 |      MASTER-Tavrida | (15h 41m 40.77s , +18d 09m 44.1s) |   C |    60 | 18.1 |        
    2649 | 2021-08-22 18:13:03 |         MASTER-SAAO | (15h 52m 16.43s , +20d 00m 45.0s) |   C |   180 | 17.8 |        
    2651 | 2021-08-22 18:14:05 |      MASTER-Tavrida | (15h 50m 00.99s , +18d 09m 09.1s) |   C |    60 | 18.0 |        
    2730 | 2021-08-22 18:15:24 |      MASTER-Tavrida | (15h 54m 45.11s , +14d 22m 04.9s) |   C |    60 | 18.1 |        
    2849 | 2021-08-22 18:16:23 |         MASTER-SAAO | (15h 40m 17.75s , +20d 03m 08.0s) |   C |   180 | 18.1 |        
    2809 | 2021-08-22 18:16:43 |      MASTER-Tavrida | (16h 03m 08.52s , +14d 21m 06.2s) |   C |    60 | 18.1 |        
    2888 | 2021-08-22 18:18:02 |      MASTER-Tavrida | (15h 52m 34.77s , +20d 02m 03.5s) |   C |    60 | 18.2 |        
    2967 | 2021-08-22 18:19:21 |      MASTER-Tavrida | (16h 01m 11.14s , +20d 02m 15.1s) |   C |    60 | 18.6 |        
    3049 | 2021-08-22 18:19:42 |         MASTER-SAAO | (15h 40m 12.49s , +20d 02m 36.6s) |   C |   180 | 18.1 |        
    3046 | 2021-08-22 18:20:40 |      MASTER-Tavrida | (16h 03m 37.00s , +16d 15m 54.0s) |   C |    60 | 18.1 |        
    3125 | 2021-08-22 18:21:59 |      MASTER-Tavrida | (16h 11m 57.21s , +16d 14m 15.4s) |   C |    60 | 18.2 |        
    3248 | 2021-08-22 18:23:02 |         MASTER-SAAO | (15h 28m 09.73s , +20d 04m 25.9s) |   C |   180 | 17.8 |        
    3204 | 2021-08-22 18:23:18 |      MASTER-Tavrida | (15h 57m 42.24s , +18d 09m 24.6s) |   C |    60 | 18.4 |        
    3283 | 2021-08-22 18:24:37 |      MASTER-Tavrida | (16h 06m 02.03s , +18d 08m 55.0s) |   C |    60 | 18.5 |        
    3362 | 2021-08-22 18:25:56 |      MASTER-Tavrida | (15h 47m 43.66s , +16d 15m 41.0s) |   C |    60 | 17.8 |        
    3448 | 2021-08-22 18:26:22 |         MASTER-SAAO | (15h 28m 17.04s , +20d 03m 32.8s) |   C |   180 | 18.0 |        
    3441 | 2021-08-22 18:27:15 |      MASTER-Tavrida | (15h 56m 09.47s , +16d 14m 42.6s) |   C |    60 | 18.0 |        
    3521 | 2021-08-22 18:28:35 |      MASTER-Tavrida | (15h 41m 34.75s , +18d 07m 32.0s) |   C |    60 | 17.7 |        
    3600 | 2021-08-22 18:29:54 |      MASTER-Tavrida | (15h 50m 07.35s , +18d 08m 01.6s) |   C |    60 | 17.8 |        
    3908 | 2021-08-22 18:34:02 |         MASTER-SAAO | (15h 44m 13.37s , +20d 01m 51.6s) |   C |   180 | 17.6 |        
    3873 | 2021-08-22 18:34:27 |      MASTER-Tavrida | (15h 52m 33.23s , +20d 03m 35.4s) |   C |    60 | 17.4 |        
    3952 | 2021-08-22 18:35:46 |      MASTER-Tavrida | (16h 01m 09.80s , +20d 02m 36.5s) |   C |    60 | 18.0 |        
    4030 | 2021-08-22 18:37:04 |      MASTER-Tavrida | (16h 03m 31.58s , +16d 13m 32.9s) |   C |    60 | 17.9 |        
    4110 | 2021-08-22 18:38:24 |      MASTER-Tavrida | (16h 11m 58.83s , +16d 13m 38.5s) |   C |    60 | 17.8 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210820A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30686
SUBJECT: GRB 210820A: Swift/UVOT Detection
DATE:    21/08/22 19:54:45 GMT
FROM:    Sam LaPorte at PSU  <sjl5346@psu.edu>

 GRB 210820A: Swift/UVOT Detection

S. J. LaPorte (PSU) and A. P. Beardmore (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210820A
131 s after the BAT trigger (Beardmore et al., GCN Circ. 30664).
A source consistent with the XRT position
(Beardmore et al., GCN Circ. 30664)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  01:22:33.48 =  20.63952 (deg.)
    Dec (J2000) = +04:36:28.3  =   4.60786 (deg.)
with an estimated uncertainty of 0.45 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

v                  437         1684          156         18.86 +/- 0.24
b                  387          555           39         18.57 +/- 0.19
u                  131          381          246         17.60 +/- 0.06
w1                 784         1733           58        >19.0

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.030 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210822A
Detection_method: Fermi LAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30687
SUBJECT: GRB 210822A: Fermi-LAT detection
DATE:    21/08/22 20:02:07 GMT
FROM:    Masanori Ohno at Hiroshima U  <ohno@astro.hiroshima-u.ac.jp>

M. Ohno (Eotvos U./Hiroshima U.), D. Kocevski (NASA/MSFC), F. Longo
(University and INFN, Trieste), a F. Dirirsa (LAPP, Annecy)
report on behalf of the Fermi-LAT Collaboration:

On August 22th, 2021, Fermi-LAT detected high-energy emission from
GRB 210822A, which was also detected by Swift-BAT (trigger1069788; Page et
al. GCN Circ. 30677) and GECAM (Wang et al., GCN Circ. 30678).


The best LAT on-ground location is found to be

RA, Dec 304.6, 4.9 (degrees, J2000)

with an error radius of 0.5 deg (90% containment, statistical error only).
This was 83 deg from the LAT boresight at the time of the Swift trigger:

T0 = 09:18:18 UT.

And the burst came into the LAT boresight about 500 s after the Swift
trigger time.
The data from the Fermi-LAT show a significant increase
in the event rate after the Swift trigger that is spatially correlated with
the Swift emission with high significance.
The photon flux above 100 MeV in the time interval 500-10000 s after the
Swift trigger is 2.5(-/+ 0.8)  ph/cm2/s.

The estimated photon index above 100 MeV is -2.4 (-/+ 0.3).

The highest-energy photon is a 1.0 GeV event which is observed 855 seconds
after the Swift trigger.

The Fermi-LAT point of contact for this burst is
Feraol F. Dirirsa (dirirsa@lapp.in2p3.fr ).

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: GRB210820A
Detection_method: correction
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30688
SUBJECT: GRB 210820A: NUTTelA-TAO / BSTI Early Optical Limits (Preliminary)
DATE:    21/08/23 00:07:17 GMT
FROM:    Bruce Grossan at LBNL/UCB SSL  <Bruce_Grossan@lbl.gov>

T. Komesh (NU), B. Grossan (UCB, NU), Z. Maksut (NU), A. Kim (NU), M. Krugov (FAI), G. F. Smoot (HKUST, UCB, NU), E. Linder (UCB, NU), E. Abdikamalov (NU) report on behalf of the Energetic Cosmos Laboratory:

The Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO) observed the field of GRB 210820A on receipt of an automated GCN / BAT position alert, observing in Sloan g', r' and i' bands, with the Burst Simultaneous Three-Channel Imager (BSTI; Grossan, Kumar & Smoot 2019, JHEA, 32, 14).

We received the alert at 17:39:26 UT (85 seconds between GRB time and notification time) and started observations at 17:39:32 UT on 2021-08-20, 6.5 s after receipt, 91 s after the BAT trigger. Observations were made under 95+% moon illumination and cloudy conditions starting at only about 20 deg. target altitude. No source consistent with the XRT or UVOT position was detected. The observations fully cover the UVOT U detection observation time (Palmer 2021, GCN 30664) and some additional UVOT observations (LaPorte 2021, GCN 30686). Note that these observations provide essentially full-time coverage, simultaneous in all three bands. We report the following results:

start time        end time        UL g'    UL r'        ULi'       exposure_time (s)
------------        -----------        ------    ------         ------      --------------------
17:39:32        17:40:32        17.0    15.1          16.4  60 
17:40:57        17:56:42        17.9    15.9   16.8         135 

UL g', r', i', gives the 5 sigma upper limit sensitivity in magnitudes in the respective filter, for images co-added to the given exposure time. The first row in the table corresponds to co-adds of an initial short exposure image sequence of 7.5 s each, the second row corresponds to co-adds from a continuing series of 15 s exposures, uninterrupted for the entire interval. No uncatalogued sources near the XRT location were found up to the co-add times indicated. Calibration was done with the few bright Pan-STARRS catalog stars on our images.

We caution the reader that these are preliminary results, without color or other corrections, and will likely change in small measure. Please also note that times are approximate. We anticipate improved analysis in 15-30 days posted at http://ecl.nu.edu.kz/gamma-ray-burst/grb210820a.

----------------------------------
NU = Nazarbayev University, Nur-Sultan, Kazakhstan
UCB = University of California, Berkeley, USA
HKUST = Hong Kong University of Science and Technology
FAI = Fesenkov Astrophysical Institute, Kazakhstan

The NUTTelA-TAO Team acknowledges the support of the staff of the Assy-Turgen Astrophysical Observatory, Almaty, Kazakhstan, and the Fesenkov Astrophysical Institute, Almaty, Kazkhstan.


GRB_name: GRB210822A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30689
SUBJECT: GRB 210822A: Swift-BAT refined analysis
DATE:    21/08/23 01:10:30 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

A. Y. Lien (U Tampa), S. D. Barthelmy (GSFC),
H. A. Krimm (NSF), S. Laha (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-240 to T+962 sec from the recent telemetry
downlink,
we report further analysis of BAT GRB 210822A (trigger #1069788)
(Page et al., GCN Circ. 30677).  The BAT ground-calculated position is
RA, Dec = 304.461, 5.265 deg which is
   RA(J2000)  =  20h 17m 50.7s
   Dec(J2000) = +05d 15' 54.9"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 64%.

The mask-weighted light curve shows a multi-peaked structure that
starts and peaks at T0. The main pulse structure ends at ~T+20 s,
followed by a long tail lasting till ~T+400 s. T90 (15-350 keV)
is 180.8 +- 42.7 sec (estimated error including systematics).

The time-averaged spectrum from T-0.37 to T+402.66 sec is best fit
by a simple power-law model.  The power law index of the time-averaged
spectrum is 1.30 +- 0.04.  The fluence in the 15-150 keV band
is 2.0 +- 0.04 x 10^-5 erg/cm2. The 1-sec peak photon flux measured
from T+0.00 sec in the 15-150 keV band is 27.7 +- 0.7 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/1069788/BA/


GRB_name: GRB210822A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30691
SUBJECT: GRB 210822A: Swift-XRT refined Analysis
DATE:    21/08/23 08:08:50 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), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), D.N.
Burrows (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester)
and K.L. Page report on behalf of the Swift-XRT team:

We have analysed 7.3 ks of XRT data for GRB 210822A (Page et al. GCN
Circ. 30677), from 64 s to 58.6 ks after the  BAT trigger. The data
comprise 1.2 ks in Windowed Timing (WT) mode (the first 9 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Evans et
al. (GCN Circ. 30682).

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=0.93 (+0.09, -0.06). At T+145 s  the decay
steepens to an alpha of 3.2 (+1.8, -0.8). The light curve breaks again
at T+157 s to a decay with alpha=1.081 (+0.016, -0.015),  again at
T+3863 s s to alpha=1.81 (+0.12, -0.11),  and  again at T+22.4 ks s to
alpha=-0.1 (+0.5, -1.4),  before a final break at T+29.6 ks s after
which the decay index is 1.7 (+/-0.3).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.829 (+/-0.019). The
best-fitting absorption column is  1.89 (+/-0.07) x 10^21 cm^-2, in
excess of the Galactic value of 1.5 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.77 (+/-0.12) and a
best-fitting absorption column of 2.3 (+/-0.5) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 4.0 x 10^-11 (5.2 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      2.3 (+/-0.5) x 10^21 cm^-2
Galactic foreground: 1.5 x 10^21 cm^-2
Excess significance: 3.1 sigma
Photon index:      1.77 (+/-0.12)

If the light curve continues to decay with a power-law decay index of
1.7, the count rate at T+24 hours will be 0.050 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.0 x
10^-12 (2.6 x 10^-12) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01069788.

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


GRB_name: GRB210822A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30692
SUBJECT: GRB 210822A: NOT photometry and spectroscopy
DATE:    21/08/23 08:25:52 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

Z.P. Zhu (NAOC, HUST), L. Izzo (DARK/NBI), S.Y.Fu, D. Xu (NAOC), J.P.U. 
Fynbo (DAWN/NBI), E. Paraskeva, S. Vitali (NOT), report on behalf of a 
larger collaboration:

We observed the bright optical afterglow of GRB 210822A (Page et al., 
GCN 30677; Wang et al., GCN 30678; Ohno et al., GCN 30687) using the 
Nordic Optical Telescope (NOT) equipped with the ALFOSC camera.

We obtained 3x120s frames in the Sloan r-filter, starting at 23:11:50 UT 
on 2021-08-22 (i.e., ~ 13.89 hr after the BAT trigger). The previously 
reported optical afterglow (e.g., Page et al., GCN 30677; Zheng & 
Filippenko, GCN 30679; Butler et al., GCN 30680; Lipunov et al., GCN 
30681; Fu et al., GCN 30684) has decayed to m(r) = 19.71 +/- 0.02, 
calibrated with the PS1 field.

Subsequently 4x1200 s spectroscopy was carried out. A continuum is 
detected over the whole wavelength range of 3700-9500 AA, superimposed 
with some absorption features, among which prominent Fe II, Mg II, Mg I, 
and Al III lines were identified at a common redshift of z = 1.736. We 
conclude that this is the redshift of the burst.


GRB_name: GRB210822A
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30693
SUBJECT: GRB 210822A: AstroSat CZTI detection
DATE:    21/08/23 09:13:47 GMT
FROM:    Gaurav Waratkar at IIT,Bombay  <gauravwaratkar@iitb.ac.in>

V. Prasad (IUCAA), P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute
(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 bright long GRB 210822A,
which was also detected by Swift (Page et al., GCN 30677), GECAM (Wang
et al., GCN 30678), and Fermi-LAT (Ohno et al., GCN 30687). 

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
2021-08-22 09:18:17.50 UT. The measured peak count rate associated with
the burst is 2190 (+85, -91) cts/s above the background in the combined
data of four quadrants, with a total of 12961 (+301, -314) cts. The
local mean background count rate was 530 (+2, -3) cts/s. Using
cumulative rates, we measure a T90 of 10 (+0.2, -0.2) 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 2021-08-22 09:18:18.97 UT. The
measured peak count rate is 3587 (+117, -127) cts/s above the background
in the combined Veto data of four quadrants, with a total of 24196
(+541, -655) cts. The local mean background count rate was 1799 (+4, -4)
cts/s. We measure a T90 of 12 (+0.5, -0.5) 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 [1]. 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. 

Links:
------
[1] http://astrosat.iucaa.in/czti/?q=grb


GRB_name: GRB210822A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30694
SUBJECT: Konus-Wind detection of GRB 210822A
DATE:    21/08/23 12:38:10 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 210822A (Swift detection: Page et al., GCN 30677;
GECAM detection: Wang et al., GCN 30678;
Fermi-LAT detection: Ohno et al., GCN 30687;
AstroSat CZTI detection: Ohno et al., GCN 30693)
triggered Konus-Wind (KW) at T0=33502.974 s UT (09:18:22.974).

The burst light curve shows a bright, multi-peaked pulse
which starts at ~T0-1 s and has a total duration of ~12 s,
followed by a weaker decaying emission visible up to ~T0+50 s.
The emission in the main pulse is seen up to ~15 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210822_T33502/

As observed by Konus-Wind, the burst had
a fluence of (1.20 Â± 0.11)x10^-4 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 0.320 s,
of (3.25 Â± 0.28)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+18.176 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 = -0.64 (-0.06,+0.07),
the high energy photon index beta = -2.39 (-0.15,+0.12),
the peak energy Ep = 398 (-29,+30) keV,
chi2 = 124/96 dof.

The spectrum near the peak count rate (measured from T0+4.096
to T0+7.936 s) is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.59 (-0.15,+0.18),
the high energy photon index beta = -2.08 (-0.18,+0.12),
the peak energy Ep = 429 (-83,+108) keV,
chi2 = 75/63 dof.

Assuming the redshift z=1.736 (Zhu et al., GCN 30692)
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 isotropic energy release E_iso to (9.5 Â± 0.8)x10^53 erg,
the isotropic luminosity L_iso to (7.0 Â± 0.6)x10^53 erg/s,
the rest-frame peak energy of the time-integrated spectrum Epi,z to (1090 Â± 80) keV,
and the rest-frame peak energy of the 'peak' spectrum Epp,z to (1175 Â± 250) keV.
With these values, GRB 210822A lies within 68% prediction bands
for both 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs
with known redshifts (Tsvetkova et al., 2021, ApJ, 908, 83),
see http://www.ioffe.ru/LEA/GRBs/GRB210702_T68826/GRB210822A_rest_frame.pdf

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


GRB_name: GRB210820A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30695
SUBJECT: GRB 210820A: GROND observations
DATE:    21/08/23 13:50:31 GMT
FROM:    Ana Nicuesa at TLS Tautenburg  <ana@tls-tautenburg.de>

A. Nicuesa Guelbenzu, S. Klose (both TLS Tautenburg) and
A. Rau (MPE Garching) report:

We observed the field of GRB 210820A (Swift trigger 1069551); Beardmore et
al., GCN 30664) simultaneously in g'r'i'z'JHK with GROND  mounted at the
2.2 m  MPG/ESO telescope at La Silla Observatory (Chile).

Observations were performed at 9:03 UT (midtime) on August 21, 2021,
about 15.5 hours  after the GRB trigger. They were executed at an
average seeing of 1.3 arcsec and at an average airmass of 1.2.

We  detect a source  within the XRT error circle (Beardmore, et al.,
GCN 30667) in the i' band with the following preliminary AB
magnitude

i'=22.46 +/- 0.28

in  agreement with the  RATIR detection (Butler et al., GCN 30672).

We do not detect the source in the other bands down to the following
limiting AB magnitudes:

g' > 22.6,

r' > 22.9,

z' > 22.3,

J > 20.9,

H > 20.4, and

K > 17.4.


The given limits and magnitude are derived based on calibrating the images
against SDSS in g'r'i'z' and 2MASS field stars in JHK.

We thank  Paul Eigenthaler  for excellent support and for performing the
observations.


GRB_name: GRB210822A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30696
SUBJECT: GRB 210822A: GECAM refined analysis
DATE:    21/08/23 15:00:34 GMT
FROM:    Chenwei Wang at IHEP  <cwwang@ihep.ac.cn>

C. W. Wang, S. L. Xiong, X. Y. Zhao, X. Y. Song, C. Cai, C. Y. Li,
Y. Huang, S. L. Xie, J. C. Liu, Y. Q. Zhang,  Y. Zhao, Z. W. Guo, C. Zheng,
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, G. X. Sun, X. L. Sun, Y. L. Tuo, J. Z. Wang,X. L. Zhang, 
W. C. Xue, X. Y. Wen, S. Xiao, 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. Wang, P. Zhang, S. N. Zhang, Z. Zhang, 
S. Y. Zhao, S. J. Zheng, X. Zhou (IHEP), report on behalf of GECAM team:

At 2021-08-22T09:18:18.00 UTC(denoted as T0), GECAM-B was triggered in-flight 
by a long bright burst, GRB 210822A, which is also observed by Swift/BAT (GCN #30677). 
The spectrum was calculated using the GECAM-B trigger data. 

The time-integrated spectrum (measured from T0 to T0+15) 
is best fit in the 20 keV - 5 MeV range 
by a power law with high energy exponential rolloff model:
dN/dE ~ (E^alpha)*exp(-E/beta)
with  alpha = -0.8595 +/- 0.029,
and beta = 394.9867 +/- 23.466 keV.

The event fluence (10-1000 keV) in this time interval is
(7.54 +0.10/-0.19)E-05 erg/cm^2. 

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: GRB210822A
Detection_method: Fermi LAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30697
SUBJECT: GRB 210822A: Detection by GRBAlpha
DATE:    21/08/23 15:42:18 GMT
FROM:    Masanori Ohno at Hiroshima U  <ohno@astro.hiroshima-u.ac.jp>

M. Ohno (Eotvos U./Konkoly Observatory/Hiroshima U.), J. Ripa (Masaryk U.),
 H. Takahashi (Hiroshima U.), A. Pal, L. Meszaros, B. Csak (Konkoly
Observatory), N. Werner, M. Topinka, F. Munz, F. Hroch (Masaryk U.), T.
Urbanec, M. Kasal,  A. Povalac (Brno U. of Technology), J. Hudec, J. Kapus,
M. Frajt (Spacemanic s.r.o), R. Laszlo, M. Koleda (Needronix s.r.o), M.
Smelko, P. Hanak, P. Lipovsky (Technical U. of Kosice), G. Galgoczi (Wigner
Research Center/Eotvos U.), Yuusuke Uchida, Helen Poon, H. Matake, N.
Uchida (Hiroshima U.), T. Bozoki (Eotvos U.), G. Dalya (Eotvos U.), T.
Enoto (Kyoto U.), Zs. Frei (Eotvos U.), G. Friss (Eotvos U.), Y. Fukazawa,
K. Hirose (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.),
K. Kapas (Eotvos U.), L. L. Kiss (Konkoly Observatory),  T. Mizuno
(Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), J.
Takatsy (Eotvos U.), K. Torigoe (Hiroshima U.) -- the GRBAlpha
collaboration.

The long duration GRB 210822A (Swift-BAT detection; Page et al. GCN Circ.
 30677, GECAM detection; Wang et al. GCN Circ. 30678, Fermi-LAT detection;
Ohno et al. GCN Circ. 30687) was detected by the GRBAlpha 1U CubeSat (Pal
et al. Proc. SPIE 2020).

The light curve shows a strong spike structure with a high significance of
a SNR ~ 45. The observed total duration was about 12 sec. GRBAlpha was
leaving the outer Van Allen radiation belt and thus GRB 210822A is
superimposed on a high background due to trapped electrons.

The light curve obtained by GRBAlpha is available here:
https://grbalpha.konkoly.hu/static/share/GRB210822A_GCN.pdf

GRBAlpha is a demonstration mission for a future CubeSats constellation
(Werner et al. Proc. SPIE 2018). The detector of GRBAlpha consists of a 75
x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy
range from ~50 keV to ~1000 keV. GRBAlpha was launched on 2021 March 22
from Baikonur. After its commissioning phase, the scientific observations
are now under way. To increase the duty cycle and the downlink rate, the
upgrade of the on-board data acquisition software stack is in progress. The
ground segment is also supported by the radio amateur community and it
takes advantage of the SatNOGS network for increased data downlink volume.


GRB_name: GRB210822B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30698
SUBJECT: GRB 210822B: DDOTI Upper Limits on the Afterglow
DATE:    21/08/23 21:39:19 GMT
FROM:    Kin O. C. L. Mendoza at Instituto de Astronoma, UNAM  <koclopez@astro.unam.mx>

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

We observed the field of the Fermi - GBM event GRB 210822B (Fermi
Collaboration, GCN Circ. 30683) with the DDOTI wide-field imager at the
Observatorio AstronÃ³mico Nacional on Sierra San Pedro Martir (
http://ddoti.astroscu.unam.mx) from 2021-08-23 05:28:21 to 06:11:11 UTC
(12.85to 13.73 hours after the trigger).

We observed a region of 20.4 degrees in RA by 20.4 degrees in declination,
with a 3 x 2 grid, centered on the Fermi GBM Final Position RA:  238.17,
DEC: +18.02 (J2000 degrees). This region contains 6 instrumental fields or
about 400 square degrees. We obtained 7.77 minutes of exposure per
instrumental field in the w filter. We obtained AB photometry by
calibration against the APASS catalog.


Comparing to the Pan-STARRS DR1 catalog, we detect no uncatalogued point
sources to a 10-sigma limiting magnitude of w = 18.07 - 18.65

We thank the staff of the Observatorio AstronÃ³mico Nacional in San Pedro
Martir.


GRB_name: GRB210824A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30699
SUBJECT: GRB 210824A: Fermi GBM Final Real-time Localization
DATE:    21/08/24 04:20:26 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 04:10:03 UT on 24 Aug 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210824A (trigger 651471008.06188 / 210824174).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 235.1, Dec = 10.4 (J2000 degrees, equivalent to J2000 15h 40m, 10d 24'), with a statistical uncertainty of 5.3 degrees.

The angle from the Fermi LAT boresight is 77.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210824174/quicklook/glg_skymap_all_bn210824174.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/bn210824174/quicklook/glg_healpix_all_bn210824174.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210824174/quicklook/glg_lc_medres34_bn210824174.gif


GRB_name: GRB210824A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30700
SUBJECT: GRB 210824A: Swift detection of a burst
DATE:    21/08/24 04:35:52 GMT
FROM:    Kim Page at U.of Leicester  <klp5@leicester.ac.uk>

K. L. Page (U Leicester), N. J. Klingler (GSFC/UMBC/CRESSTII),
H. A. Krimm (NSF), A. Y. Lien (U Tampa), M. H. Siegel (PSU) and
A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 04:10:01 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210824A (trigger=1070157).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 232.132, +11.135 which is 
   RA(J2000) = 15h 28m 32s
   Dec(J2000) = +11d 08' 07"
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 50 sec.  The peak count rate
was ~1600 counts/sec (15-350 keV), at ~3 sec after the trigger. 

The XRT began observing the field at 04:15:08.4 UT, 306.9 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source located at RA, Dec 232.10513, 11.15208 which
is equivalent to:
   RA(J2000)  = 15h 28m 25.23s
   Dec(J2000) = +11d 09' 07.5"
with an uncertainty of 7.2 arcseconds (radius, 90% containment). This
location is 113 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 (3.31 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 8.5
(+5.30/-4.44) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 310 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 none of
the XRT error circle. 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 0.036. 

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: GRB210822A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30701
SUBJECT: GRB 210822A: Abbey Ridge Observatory optical afterglow observation
DATE:    21/08/24 06:49:06 GMT
FROM:    Filipp Dmitrievich Romanov at Amateur astronomer  <filipp.romanov.27.04.1997@gmail.com>

Filipp D. Romanov (Russia) and David J. Lane (Saint Mary's University,
Canada) report:

Filipp Romanov observed optical afterglow of GRB 210822A (Page et al.,
GCN Circ. 30677) remotely using 0.355-m f/6.2 Schmidt-Cassegrain
telescope of Abbey Ridge Observatory (it is owned by Dave Lane) in
Canada, on 2021-08-23.

Four images (with exposures: 720, 720, 600 and 720 seconds) were
obtained with Cousins R filter from 00:54:39 to 02:17:30 UTC. Faint
(SNR = 5) optical afterglow (with UVOT position) is visible in the
stacked image (mid time =  01:36:04 UTC, that is 16.296 hours after
the trigger). Romanov measured its magnitude comparing to transformed
(using formula Rc=râ€™-0.22 from Dymock & Miles, 2009) r' magnitudes of
nearby stars from Pan-STARRS DR1 catalogue (Chambers et al., 2016).
The measured magnitude = 20.1 +/- 0.3. Magnitude was not corrected for
Galactic extinction.

Stacked image available here:
http://abbeyridgeobservatory.ca/images/grb210822a.jpg


GRB_name: GRB210824A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30702
SUBJECT: GRB 210824A: Enhanced Swift-XRT position
DATE:    21/08/24 11:40:54 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 1505 s of XRT Photon Counting mode data and 3 UVOT
images for GRB 210824A, 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 = 232.10583, +11.15351 which is equivalent
to:

RA (J2000): 15h 28m 25.40s
Dec (J2000): +11d 09' 12.6"

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: GRB210822A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30703
SUBJECT: GRB 210822A: GROND observations
DATE:    21/08/24 15:19:39 GMT
FROM:    Ana Nicuesa at TLS Tautenburg  <ana@tls-tautenburg.de>

A. Nicuesa Guelbenzu, S. Klose (both TLS Tautenburg) and
A. Rau (MPE Garching) report:


We observed the field of GRB 210822A (Swift trigger #1069788; Page et al.,
GCN 30677) with GROND mounted at the 2.2m MPG telescope at La Silla
Observatory (Chile).

Observations started at 02:54 UT on August 23, about 17.6 hr after the GRB
trigger. They were performed at an average seeing of 2.2 arcsec and at an
average airmass of 1.2.

Based on combined images with 10 min total exposure, at a mid-time of
03:02 UT on 2021-08-23 for the afterglow (Page et al., GCN 30677; Zheng &
Filippenko, GCN 30679; Butler et al., GCN 30680; Fu et al., GCN 30684; Zhu
et al., GCN 30692; Romanov & Lane, GCN 30701) we derive the following
AB magnitudes:

g' = 20.37 +/- 0.09,
r' = 20.10 +/- 0.05,
i' = 19.92 +/- 0.05.

Given magnitudes are calibrated against Pan-STARRS and   are not corrected
for the expected Galactic foreground extinction corresponding to a
reddening of E(B-V) = 0.14 mag in the direction of the burst (Schlegel et
al. 1998).

We thank Angela Hempel for excellent support and for performing the
observations.


GRB_name: GRB210824A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30704
SUBJECT: GRB 210824A: Swift-XRT refined Analysis
DATE:    21/08/24 15:28:01 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

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

We have analysed 6.6 ks of XRT data for GRB 210824A (Page et al. GCN
Circ. 30700), from 320 s to 28.9 ks after the  BAT trigger. The data
are entirely in Photon Counting (PC) mode. The enhanced XRT position
for this burst was given by Goad et al. (GCN Circ. 30702).

The late-time light curve (from T0+3.9 ks) can be modelled with a
power-law decay with a decay index of alpha=0.94 (+0.25, -0.23).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.4 (+/-0.4). The
best-fitting absorption column is  6.8 (+3.1, -2.3) x 10^21 cm^-2, in
excess of the Galactic value of 3.3 x 10^20 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 (8.4 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      6.8 (+3.1, -2.3) x 10^21 cm^-2
Galactic foreground: 3.3 x 10^20 cm^-2
Excess significance: 4.6 sigma
Photon index:      2.4 (+/-0.4)

If the light curve continues to decay with a power-law decay index of
0.94, the count rate at T+24 hours will be 2.4 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.5 x
10^-14 (2.0 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/01070157.

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


GRB_name: GRB210824A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30705
SUBJECT: GRB 210824A: Nanshan/NEXT optical upper limit
DATE:    21/08/24 16:06:10 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

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

We observed the field of Swift GRB 210824A (Page et al. GCN Circ. 30700) 
using the NEXT-0.6m telescope located at Nanshan, Xinjiang, China. We 
obtained 10x200 s frames in the Sloan r-band, starting at 14:54:25 UT on 
2021-08-24, i.e., 10.74 hr after the BAT trigger.

No optical source is detected in our stacked image at the enhanced 
Swift/XRT position (Goad et al., GCN 30702), down to a limiting 
magnitude of r~21.1, calibrated with the nearby PanSTARRS field.


GRB_name: GRB210824A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30706
SUBJECT: Fermi GRB 210824A: Global MASTER-Net observations report 
DATE:    21/08/24 17:01:04 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 210824A ( Fermi GBM team, GCN 30699) errorbox  45625 sec after notice time and 45651 sec after trigger time at 2021-08-24 16:50:54 UT, with upper limit up to  17.2 mag. Observations started at twilight.  The observations began at zenith distance = 46 deg. The sun  altitude  is -7.8 deg. 

The galactic latitude b = 46 deg., longitude l = 19 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1698440

We obtain a following upper limits.  

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

   45682 | 2021-08-24 16:50:54 |         MASTER-SAAO | (15h 30m 37.82s , +12d 36m 58.0s) |   C |    60 | 16.0 |        
   45762 | 2021-08-24 16:52:14 |         MASTER-SAAO | (15h 38m 47.90s , +12d 35m 22.7s) |   C |    60 | 16.6 |        
   45841 | 2021-08-24 16:53:34 |         MASTER-SAAO | (15h 24m 16.66s , +10d 42m 42.8s) |   C |    60 | 17.0 |        
   45921 | 2021-08-24 16:54:54 |         MASTER-SAAO | (15h 32m 23.86s , +10d 43m 21.8s) |   C |    60 | 17.2 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210824A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30707
SUBJECT: GRB 210824A: Fermi GBM Observation
DATE:    21/08/24 19:45:52 GMT
FROM:    Stephen Lesage at Fermi-GBM Team  <sjl0014@uah.edu>

S. Lesage (UAH) reports on behalf of the Fermi Gamma-ray Burst Monitor Team:

"At 04:10:03 UT on 24 August 2021, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 210824A (trigger 651471008/210824174)
which was also detected by Swift BAT (K. L. Page et al. 2021, GCN 30700).
The Fermi GBM Final Real-time Localization (GCN 30699) is consistent
with the Swift BAT position.

The angle from the Fermi LAT boresight is 75 degrees.

The GBM light curve consists of a single emission episode with a duration (T90)
of about 33 s (10-1000 keV). The time-averaged spectrum
from T0-0.6 to T0+28 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.2 +/- 0.1 and the cutoff energy,
parameterized as Epeak, is 552 +/- 286 keV.

The event fluence (10-1000 keV) in this time interval is
(5.3 +/- 0.6)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+4.1 s in the 10-1000 keV band is 2.2 +/- 0.2 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: GRB210824A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30708
SUBJECT: GRB 210824A: BOOTES-5/JGT optical upper limit
DATE:    21/08/24 21:59:55 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

Y.-D. Hu, T.-R. Sun, E. Fernandez-Garcia, A. J. Castro-Tirado and M.D. Caballero-Garcia (IAA-CSIC), D. Hiriart, W. H. Lee (UNAM), C. J. Perez del Pulgar and I. Carrasco (UMA), I. H. Park (SKKU) on behalf of a larger collaboration, report:

The 60cm BOOTES-5/JGT robotic telescope at Observatorio Astronomico Nacional in San Pedro Martir (Mexico) automatically responded in 54 s to the Swift trigger of GRB 210824A (Page et al., GCNC 30700) , a burst which was also detected by Fermi (Fermi GBM team, GCNC 30699). In the co-added clear image (10 x 10 s), no optical afterglow is detected within the X-ray afterglow position (Page et al., GCNC 30700; Goad et al., GCNC 30702) down to 19.9 mag.

We thank the staff at Observatorio Astronomico Nacional in San Pedro Martir for its excellent support.


GRB_name: GRB210824A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30709
SUBJECT: Swift GRB 210824A: Global MASTER-Net observations report 
DATE:    21/08/25 04:10:10 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) was pointed to the Swift GRB 210824A ( K. L. Page et al., GCN 30700) errorbox  45612 sec after notice time and 45332 sec after trigger time at 2021-08-24 16:50:54 UT, with upper limit up to  19.4 mag. Observations started at twilight.  The observations began at zenith distance = 46 deg. The sun  altitude  is -7.8 deg. 

MASTER-Tavrida robotic telescope  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the Swift GRB 210824A errorbox  48172 sec after notice time and 47892 sec after trigger time at 2021-08-24 17:33:34 UT, with upper limit up to  19.1 mag. Observations started at twilight.  The observations began at zenith distance = 47 deg. The sun  altitude  is -10.9 deg. 

MASTER-Kislovodsk robotic telescope  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 210824A errorbox  50320 sec after notice time and 50041 sec after trigger time at 2021-08-24 18:09:23 UT, with upper limit up to  17.4 mag. The observations began at zenith distance = 56 deg. The sun  altitude  is -21.7 deg. 

The galactic latitude b = 49 deg., longitude l = 17 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1698433

We obtain a following upper limits.  

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

   45363 |         MASTER-SAAO |   C |    60 | 16.0 |        
   45522 |         MASTER-SAAO |   C |    60 | 17.0 |        
   45602 |         MASTER-SAAO |   C |    60 | 17.2 |        
   46324 |         MASTER-SAAO |   C |    60 | 18.5 |        
   46483 |         MASTER-SAAO |   C |    60 | 18.7 |        
   46563 |         MASTER-SAAO |   C |    60 | 18.8 |        
   47281 |         MASTER-SAAO |   C |    60 | 19.4 |        
   47440 |         MASTER-SAAO |   C |    60 | 19.3 |        
   47520 |         MASTER-SAAO |   C |    60 | 19.4 |        
   47983 |      MASTER-Tavrida |   C |   180 | 17.8 |        
   49103 |      MASTER-Tavrida |   C |   180 | 19.1 |        
   49875 |      MASTER-Tavrida |   C |    60 | 18.7 |        
   50071 |   MASTER-Kislovodsk |   C |    60 | 15.8 |        
   50252 |      MASTER-Tavrida |   C |   180 | 19.0 |        
   50310 |   MASTER-Kislovodsk |   C |   180 | 15.1 |        
   50310 |   MASTER-Kislovodsk |   C |   180 | 15.3 |        
   51024 |      MASTER-Tavrida |   C |    60 | 18.4 |        
   51479 |      MASTER-Tavrida |   C |    60 | 18.4 |        
   51558 |      MASTER-Tavrida |   C |    60 | 18.4 |        
   52080 |   MASTER-Kislovodsk |   C |    60 | 16.6 |        
   52268 |         MASTER-SAAO |   C |    60 | 18.8 |        
   52527 |      MASTER-Tavrida |   C |    60 | 18.1 |        
   52605 |      MASTER-Tavrida |   C |    60 | 18.1 |        
   53102 |   MASTER-Kislovodsk |   C |   180 | 17.1 |        
   53102 |   MASTER-Kislovodsk |   C |   180 | 17.4 |        
   53227 |         MASTER-SAAO |   C |    60 | 18.6 |        
   53242 |   MASTER-Kislovodsk |   C |    60 | 17.0 |        
   53476 |      MASTER-Tavrida |   C |    60 | 17.9 |        
   53555 |      MASTER-Tavrida |   C |    60 | 17.9 |        
   54344 |   MASTER-Kislovodsk |   C |   180 | 17.0 |        
   54344 |   MASTER-Kislovodsk |   C |   180 | 17.1 |        
   54478 |      MASTER-Tavrida |   C |   180 | 18.0 |        
   54482 |         MASTER-SAAO |   C |   180 | 18.5 |        
   54617 |      MASTER-Tavrida |   C |    60 | 17.6 |        
   55565 |         MASTER-SAAO |   C |   180 | 17.0 |        
   55613 |      MASTER-Tavrida |   C |   180 | 17.8 |        
   55831 |      MASTER-Tavrida |   C |    60 | 17.5 |        
   56489 |   MASTER-Kislovodsk |   C |    60 | 12.8 |        
   56489 |   MASTER-Kislovodsk |   C |    60 | 14.0 |        
   56723 |         MASTER-SAAO |   C |   180 | 15.9 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210822A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30710
SUBJECT: GRB 210822A: Swift/UVOT Detection
DATE:    21/08/25 06:21:36 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M. H. Siegel (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 210822A
85 s after the BAT trigger (Page et al., GCN Circ. 30677).
A fading source consistent with the XRT position (Page et al.
GCN Circ. 30677) and the previously reported UVOT source is 
is detected in the initial UVOT exposures.

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 (fc)          86          236          147      13.63+/-1.10
white              577         1200          205      15.35+/-0.02
white             4965         5058           91      17.43+/-0.05
white            34405        35230          804      19.15+/-0.05
white           149533       190336         1894      20.64+/-0.11
v                  627         1250           77      15.07+/-0.05
v                27494        28215          702      18.68+/-0.13
b                  553         1176           58      15.31+/-0.04
b                 4760         4960          196      17.56+/-0.06
b                33493        34400          885      19.18+/-0.08
u (fc)             298          548          245      13.78+/-0.03
u                  700         1304           39      14.86+/-0.05
u                 4555         4755          196      16.85+/-0.05
u                57947        58635          670      19.73+/-0.19
uvw1               676         1299           77      15.28+/-0.07
uvw1             39434        96567         1775      19.90+/-0.22
uvm2               824         1274           38            >17.66
uvm2             92215        93015          788            >20.06
uvw2               602         1225           77      17.21+/-0.18
uvw2             21659        64335         1469      20.40+/-0.34

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.162 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210822A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30712
SUBJECT: GRB 210822A: TSHAO optical observation
DATE:    21/08/25 09:49:39 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI), A. Kusakin (FAP), I. Reva (FAP),  Pozanenko (IKI), N. 
Pankov (HSE), V. Kim (FAP) report on behalf of GRB-IKI-FuN:

We observed GRB 210822A (Page et al., GCN  30677;  Wang et al., GCN 
30678; Prasad  et al., GCN  30693; Frederiks et al., GCN 30694) with 
Zeiss-1000 telescope of Tien Shan Astronomical Observatory on Aug. 22 
(UT) 15:48:55 -- 18:48:47. We obtained series with 20 and 30 sec 
exposition in R-filter.

The optical afterglow (Page et al., GCN  30677; Zheng et al., GCN 30679; 
Butler et al., GCN 30680; Fu et al., GCN 30684; Zhu  et al., GCN 30692; 
Romanov  et al., GCN 30701; Guelbenzu et al., GCN 30703; Siegel et al., 
GCN 30710) at redshift z = 1.736 (Zhu  et al., GCN 30692) is detected in 
stacked images. Preliminary photometry of the afterglow in a stacked 
image of the second series is following.

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

2021-08-22 17:26:41 0.36184  R      196*20 18.63 0.03 21.0

The photometry is based on nearby USNO-B1.0 stars.

USNO-B1.0
RA Dec R2
20:18:06.64416 +05:17:24.1404 12.33
20:17:59.55288 +05:18:19.5912 13.05


GRB_name: GRB210822A
Detection_method: VLA Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30713
SUBJECT: GRB 210822A: VLA detection
DATE:    21/08/25 14:47:06 GMT
FROM:    Tanmoy Laskar at U of Bath  <tanmoylaskar@gmail.com>

T. Laskar (University of Bath), K. D. Alexander (Northwestern), E. Berger
(Harvard), R. Chornock (UC Berkeley), W. Fong (Northwestern), R. Margutti
(UC Berkeley), C. G. Mundell (University of Bath), P. Schady (University of
Bath), and G. Schroeder (Northwestern) report on behalf of a larger
collaboration:

"We observed GRB 210822A (Page et al. GCN 30677) with the Karl G. Jansky
Very Large Array (VLA) beginning on 2021 August 24 at 05:30 UT (1.9 d after
the burst). At a mean frequency of 14.8 GHz, we detect a radio source with
a preliminary flux density of ~ 0.4 mJy at the position:

RA (J2000) = 20:17:44.992 +/- 0.001
Dec (J2000) = 05:16:59.53 +/- 0.02

consistent with the position of the optical afterglow (Page et al., GCN
30677) and the Swift/XRT afterglow (Evans al., GCN 30682). Follow-up
observations are planned.

We thank the VLA staff for rapidly executing these observations."


GRB_name: GRB210822A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30714
SUBJECT: GRB 210822A: TSHAO continued optical observation
DATE:    21/08/25 16:34:52 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI), A. Kusakin (FAP), I. Reva (FAP),  Pozanenko (IKI), N. 
Pankov (HSE), V. Kim (FAP) report on behalf of GRB-IKI-FuN:

We continue observations of GRB 210822A (Page et al., GCN  30677;  Wang 
et al., GCN 30678; Prasad  et al., GCN  30693; Frederiks et al., GCN 
30694) with Zeiss-1000 telescope of Tien Shan Astronomical Observatory. 
on Aug. 22 (UT) 15:48:55 -- 18:48:47. We obtained series  in R-filter 
starting on  2021-08-24 (UT) 16:47:35.

The optical afterglow (Page et al., GCN  30677; Zheng et al., GCN 30679; 
Butler et al., GCN 30680; Fu et al., GCN 30684; Zhu  et al., GCN 30692; 
Romanov  et al., GCN 30701; Guelbenzu et al., GCN 30703; Siegel et al., 
GCN 30710; Belkin  et al., GCN 30712) at the redshift of z = 1.736 (Zhu 
  et al., GCN 30692) is detected in stacked image. Preliminary 
photometry of the afterglow in a stacked image is following.

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

2021-08-24 16:47:35 2.33041  R      3180  21.60 0.26  22.0

The photometry is based on nearby USNO-B1.0 stars.

USNO-B1.0
RA Dec R2
20:18:06.64416 +05:17:24.1404 12.33
20:17:59.55288 +05:18:19.5912 13.05


GRB_name: GRB210826A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30716
SUBJECT: GRB 210826A: Fermi GBM Final Real-time Localization
DATE:    21/08/26 07:12:03 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 07:01:45 UT on 26 Aug 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210826A (trigger 651654110.161386 / 210826293).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 64.6, Dec = -77.1 (J2000 degrees, equivalent to J2000 04h 18m, -77d 05'), with a statistical uncertainty of 2.1 degrees.

The angle from the Fermi LAT boresight is 48.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210826293/quicklook/glg_skymap_all_bn210826293.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/bn210826293/quicklook/glg_healpix_all_bn210826293.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210826293/quicklook/glg_lc_medres34_bn210826293.gif


GRB_name: GRB210826A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30717
SUBJECT: GRB 210826A: BALROG localization (Fermi Trigger 651654110 / GRB 210826293)
DATE:    21/08/26 07:41:33 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
651654110 at 07:01:45 on 26 Aug. 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) = 84.3+/-5.4 deg
Decl.(2000.0) = -75.6+/-0.7 deg
We estimate an additional systematic error of 2 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210826293/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210826293/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210826293/json

                        


GRB_name: GRB210824A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30718
SUBJECT: GRB 210824A: MITSuME Akeno optical upper limits
DATE:    21/08/26 09:48:44 GMT
FROM:    Masafumi Niwano at Tokyo Institute of Tech  <niwano@hp.phys.titech.ac.jp>

M. Niwano, K. L. Murata, R. Hosokawa, N. Ito, Y. Imai, H. Takamatsu, R. 
Noto, S. Sato, M. Takaku, R. Yamaguchi, Y. Yatsu, and N. Kawai 
(TokyoTech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 210824A (Fermi GBM team, GCN Circular 
#30699, K. L. Page et al. GCN Circular #30700, M.R. Goad et al. GCN 
Circular #30702, V. D'Elia et al. GCN Circular #30704, X. Liu et al. GCN 
Circular #30705, V. Lipunov et al. GCN Circular #30706, S. Lesage et al. 
GCN Circular #30707, Y.-D. Hu et al. GCN Circular #30708, V. Lipunov et 
al. GCN Circular #30709) with the optical three color (g', Rc, and Ic) 
CCD cameras attached to the MITSuME 50 cm telescope Akeno. The 
observation with a series of 60 sec exposures started at 2021-08-25 
10:20:44 UT (30.1 hours after Fermi trigger). We stacked the images with 
good conditions. We did not detect any uncatalogued sources within the 
XRT error region (V. D'Elia et al. GCN Circular #30706). We obtained the 
5-sigma limits of the stacked images as follows.

T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------ 

31.3 2021-08-25 12:29:20.71 4740 g'>18.6, Rc>19.0, Ic>18.3
------------------------------------------------------------------------------------------------ 

T0+ : Elapsed time after the burst
T-EXP: Total Exposure time

We used 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: GRB210826A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30719
SUBJECT: GRB 210826A: Tiled Swift observations
DATE:    21/08/26 17:11:02 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 series of observations, tiled on the sky, of the
Fermi/LAT GRB 210826A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00101

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of finding
serendipitous sources, unrelated to the Fermi/LAT event is high: 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: GRB210826A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30720
SUBJECT: Fermi GRB 210826A: Global MASTER-Net observations report 
DATE:    21/08/26 17:30:25 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 210826A ( Fermi GBM team, GCN 30716) errorbox  36801 sec after notice time and 36879 sec after trigger time at 2021-08-26 17:16:24 UT, with upper limit up to  17.8 mag. Observations started at twilight.  The observations began at zenith distance = 71 deg. The sun  altitude  is -13.0 deg. 

The galactic latitude b = -35 deg., longitude l = 291 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1700544

We obtain a following upper limits.  

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

   36909 | 2021-08-26 17:16:24 |         MASTER-SAAO | (05h 11m 37.00s , -76d 38m 26.5s) |   C |    60 | 17.8 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210826A
Detection_method: Fermi LAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30721
SUBJECT: GRB 210826A: Fermi-LAT detection
DATE:    21/08/26 19:15:46 GMT
FROM:    Masanori Ohno at Hiroshima U  <ohno@astro.hiroshima-u.ac.jp>

M. Ohno (Eotvos U./Hiroshima U.), M. Axelsson (KTH & Stockholm Univ.), F.
Longo (University and INFN, Trieste),
N. Omodei (Stanford Univ.) and F Dirirsa (LAPP, Annecy) report on behalf of
the Fermi-LAT Collaboration:

On August 26th, 2021, Fermi-LAT detected high-energy emission from
GRB 210826A, which was also detected by Fermi GBM (trigger 651654110.161386
/ 210826293; GCN 30716).

The best LAT on-ground location is found to be

RA, Dec 45.3, -71.7 (degrees, J2000)

with an error radius of 0.2 deg (90% containment, statistical error only).
This was 55 deg from the LAT boresight at the time of the GBM trigger:

T0 = 07:01:45 UT.

The data from the Fermi-LAT show a significant increase in the event rate
after the trigger that is spatially correlated with the GBM emission with
high
significance. The photon flux above 100 MeV in the time interval 0-4000 s
after the trigger is 9.3 (-/+ 3.8) e-07  ph/cm2/s.

The estimated photon index above 100 MeV is -1.9 (-/+ 0.3).

The highest-energy photon is a 7.7 GeV event which is observed ~2.6 ks
after the trigger.

A Swift ToO has been approved for this burst.

The Fermi-LAT point of contact for this burst is
Feraol Fana Dirirsa (dirirsa@lapp.in2p3.fr).

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: GRB210824A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30722
SUBJECT: GRB 210824A: Swift-BAT refined analysis
DATE:    21/08/26 19:38:20 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm@nsf.gov>

C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), K. L. Page (U Leicester),
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 210824A (trigger #1070157)
(Page, et al., GCN Circ. 30700).  The BAT ground-calculated position is
RA, Dec = 232.115, 11.169 deg which is 
 RA(J2000)  =  15h 28m 27.5s 
 Dec(J2000) = +11d 10' 09.9" 
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 60%.

The mask-weighted light curve shows a single broad pulse with some sub-structure.
It begins around T-15 sec, peaks at the trigger time and decays to background by
T+40 sec.  We note that the light curve has a gap from T+110 sec to T+240 sec due to the
burst going out of the field of view (for a pre-planned slew that started before the trigger 
had been fully processed) and then coming back into FOV when the pre-planned slew ended 
and the automated target slew had started.  The burst appears to be over before this time.   
T90 (15-350 keV) is 37.55 +- 4.79 sec (estimated error including systematics).

The time-averaged spectrum from T-13.70 to T+30.94 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.18 +- 0.11.  The fluence in the 15-150 keV band is 1.7 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+1.02 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
http://gcn.gsfc.nasa.gov/notices_s/1070157/BA/


GRB_name: GRB210822A
Detection_method: Fermi LAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30723
SUBJECT: GRB 210822A: CAHA 2.2m observations
DATE:    21/08/27 00:27:10 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. Thoene, M. Blazek, J. F. Agui Fernandez (all 
HETH/IAA-CSIC), A. Fernandez, I. Hermelo, and P. Martin (all CAHA) 
report:

We observed the bright GRB 210822A (Swift detection: Page et al., GCN 
#30677; GECAM detection: Wang et al., GCN #30678; Fermi-LAT detection: 
Ohno et al., GCN #30687;  AstroSat CZTI detection: Prasad et al., GCN 
#30693; Konus-Wind detection: Frederiks et al., GCN #30694; GRBAlpha 
detection: Ohno et al., GCN #30697) at a redshift of z = 1.736 (Zhu et 
al., GCN #30692) with CAFOS mounted on the 2.2m CAHA telescope at Calar 
Alto, Alemria, Spain. The first epoch was obtained under very inclement 
conditions (almost overcast), and one 60 s as well as four 90 s images 
were useful. The second epoch, two nights later, was obtained under 
significantly improved (but still not really good) conditions, and 31 x 
30 s images were obtained.

The optical afterglow (Page et al., GCN #30677; Zheng et al., GCN 
#30679; Butler et al., GCN #30680; Fu et al., GCN #30684; Zhu  et al., 
GCN #30692; Romanov & Lane, GCN #30701; Nicuesa Guelbenzu et al., GCN 
#30703; Siegel et al., GCN #30710; Belkin  et al., GCN #30712; Belkin  
et al., GCN #30714) is faintly detected in the first epoch, but not 
detected in the second epoch.

Against three nearby Pan-STARRS comparison stars, we measure (AB 
magnitudes):

i' = 18.56 +/- 0.14 mag at 0.43283 days after the GRB, and
i' > 21.5 mag at 2.5206 mag after the GRB.


GRB_name: GRB210827A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30724
SUBJECT: GRB 210827A: Fermi GBM Final Real-time Localization
DATE:    21/08/27 10:09:47 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 09:59:24 UT on 27 Aug 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210827A (trigger 651751169.343218 / 210827416).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 138.3, Dec = 60.2 (J2000 degrees, equivalent to J2000 09h 13m, 60d 12'), with a statistical uncertainty of 20.2 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/bn210827416/quicklook/glg_skymap_all_bn210827416.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/bn210827416/quicklook/glg_healpix_all_bn210827416.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210827416/quicklook/glg_lc_medres34_bn210827416.gif


GRB_name: GRB210826A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30725
SUBJECT: GRB 210826A: Swift-XRT observations
DATE:    21/08/27 10:16:23 GMT
FROM:    Paolo D'Avanzo at INAF - OAB  <paolo.davanzo@inaf.it>

A. D'Ai (INAF-IASFPA), B. Sbarufatti (PSU), D.N. Burrows (PSU), J. D.
Gropp (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester),
A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAB), T. Sbarrato
(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
Fermi/LAT-detected burst GRB 210826A (Ohno et al. GCN Circ. 30721), for
a total exposure time of 4.9 ks. The data were collected between
T0+36.5 ks and T0+49.7 ks, and are entirely in Photon Counting (PC)
mode.

Eight uncatalogued X-ray sources have been detected, however none of
them is above the RASS limit or shows definitive signs of fading.
Therefore, at the present time we cannot identify which, if any, is the
afterglow. We notice that one of the sources (Source 8) is consistent
with a catalogued galaxy at redshift z = 0.05. Details of these sources
are given below:

Source 1:
  RA (J2000):  45.3361  =  03:01:20.66
  Dec (J2000): -71.7072  =  -71:42:25.8
  Error: 8.7 arcsec (radius, 90% conf.)
  Count-rate: (1.46 [+0.80, -0.61])e-3 ct s^-1  
  Distance: 48 arcsec from Fermi/LAT position.

Source 2:
  RA (J2000):  45.0955  =  03:00:22.93
  Dec (J2000): -71.6531  =  -71:39:11.1
  Error: 5.0 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: (3.06 [+1.16, -0.94])e-3 ct s^-1  
  Distance: 286 arcsec from Fermi/LAT position.
  Flux: (8.2 [+3.1, -2.5])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 4:
  RA (J2000):  45.1820  =  03:00:43.67
  Dec (J2000): -71.5711  =  -71:34:15.8
  Error: 9.7 arcsec (radius, 90% conf.)
  Count-rate: (1.36 [+0.80, -0.59])e-3 ct s^-1  
  Distance: 483 arcsec from Fermi/LAT position.
  Flux: (8.2 [+4.8, -3.6])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)
This source is 10" away from  the AGN candidate WISEA
J030045.23-713422.8 (Assef et al., 2018, ApJS, 234, 23)

Source 5:
  RA (J2000):  45.4777  =  03:01:54.65
  Dec (J2000): -71.6539  =  -71:39:13.9
  Error: 8.4 arcsec (radius, 90% conf.)
  Count-rate: (3.7 [+1.3, -1.0])e-3 ct s^-1   
  Distance: 260 arcsec from Fermi/LAT position.
  Flux: (5.8 [+2.0, -1.6])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 6:
  RA (J2000):  45.1850  =  03:00:44.41
  Dec (J2000): -71.7836  =  -71:47:00.9
  Error: 10.0 arcsec (radius, 90% conf.)
  Count-rate: (1.60 [+0.86, -0.65])e-3 ct s^-1  
  Distance: 327 arcsec from Fermi/LAT position.
  Flux: (4.2 [+2.2, -1.7])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 7:
  RA (J2000):  45.3683  =  03:01:28.39
  Dec (J2000): -71.6617  =  -71:39:42.1
  Error: 10.3 arcsec (radius, 90% conf.)
  Count-rate: (1.54 [+0.84, -0.63])e-3 ct s^-1  
  Distance: 158 arcsec from Fermi/LAT position.
This source is 6" away from  the AGN candidate WISEA
J030129.33-713938.6 (Assef et al., 2018, ApJS, 234, 23)

Source 8:
  RA (J2000):  44.7903  =  02:59:9.68
  Dec (J2000): -71.6112  =  -71:36:40.2
  Error: 9.3 arcsec (radius, 90% conf.)
  Count-rate: (1.11 [+0.78, -0.56])e-3 ct s^-1  
  Distance: 660 arcsec from Fermi/LAT position.
This source is 9" away from the catalogued galaxy 2MASX
J02591150-7136430 at redshift z = 0.05

Source 9:
  RA (J2000):  45.6834  =  03:02:44.02
  Dec (J2000): -71.6574  =  -71:39:26.7
  Error: 8.8 arcsec (radius, 90% conf.)
  Count-rate: (2.16 [+1.02, -0.79])e-3 ct s^-1  
  Distance: 460 arcsec from Fermi/LAT position.
  Flux: (8.1 [+3.8, -3.0])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

The results of the XRT-team automatic analysis of the tiled XRT
observations, including a position-specific upper limit calculator, are
available at https://www.swift.ac.uk/xrt_products/TILED_GRB00101.

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


GRB_name: GRB210827B
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30726
SUBJECT: GRB 210827B: Fermi GBM Final Real-time Localization
DATE:    21/08/27 10:20:35 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 10:10:16 UT on 27 Aug 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210827B (trigger 651751821.143562 / 210827424).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 308.8, Dec = -19.3 (J2000 degrees, equivalent to J2000 20h 35m, -19d 18'), with a statistical uncertainty of 2.5 degrees.

The angle from the Fermi LAT boresight is 66.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210827424/quicklook/glg_skymap_all_bn210827424.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/bn210827424/quicklook/glg_healpix_all_bn210827424.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210827424/quicklook/glg_lc_medres34_bn210827424.gif


GRB_name: GRB210827B
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30727
SUBJECT: GRB 210827B: BALROG localization (Fermi Trigger 651751821 / GRB 210827424)
DATE:    21/08/27 10:28:30 GMT
FROM:    Jochen Greiner at MPE,Garching  <jcg@mpe.mpg.de>

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

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
651751821 at 10:10:16 on 27 Aug. 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) = 305.1+/-2.9 deg
Decl.(2000.0) = -17.3+/-2.3 deg
We estimate an additional systematic error of 1 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210827424/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210827424/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210827424/json

                        


GRB_name: GRB210826A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30729
SUBJECT: GRB 210826A: Swift/UVOT Upper Limits
DATE:    21/08/27 15:38:05 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and T. Sbarrato (INAF-IASFPA) report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210826A 36747 s after the LAT trigger 
(Ohno et al., GCN Circ. 30721). No new optical source consistent with the any of the 8 candidate XRT 
positions (D'Ai et al., GCN Circ. 30725) 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 initial exposures are:

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

v                36747        49716         4869         >20.9

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of 
E(B-V) = 0.032 in the direction of the burst (Schlegel et al. 1998).


GRB_name: GRB210824A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30730
SUBJECT: GRB 210824A: Swift/UVOT Upper Limits
DATE:    21/08/27 15:52:44 GMT
FROM:    Sam LaPorte at PSU  <sjl5346@psu.edu>

 GRB 210824A: 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 210824A
311 s after the BAT trigger (Page et al., GCN Circ. 30700).
No optical afterglow consistent with the XRT position
(Goad et al. GCN Circ. 30702)
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           311          461          147         >20.8
white              311         4350          364         >20.9
v                  467         4760          236         >19.4
b                  565         4145          235         >20.1
u                  541         5220           83         >19.6
w1                 516         5170          236         >20.4
m2                4765         4965          197         >20.3
w2                4356         4555          197         >19.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.037 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210820A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30731
SUBJECT: GRB 210820A: CAHA 2.2m Optical Detection
DATE:    21/08/27 18:03:36 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. Thoene, M. Blazek, J. F. Agui Fernandez (all 
HETH/IAA-CSIC), A. Fernandez, and I. Hermelo (all CAHA) report:

We observed GRB 210820A (Swift detection: Beardmore et al., GCN #30664) 
with CAFOS mounted on the 2.2m CAHA telescope at Calar Alto, Alemria, 
Spain, under inclement conditions (bright moonlight, passing clouds, low 
transparency). We obtained 10 x 90 s each in filters B, V, Rc. Stacks 
reveal no detection of the afterglow in B (very shallow because of 
moonlight) and Rc (shallow because of incoming clouds which also 
prevented further observations). However, the afterglow (Beardmore et 
al., GCN #30664; Butler et al., GCN #30672; LaPorte & Beardmore, GCN 
#30686; Nicuesa Guelbenzu et al., GCN #30695) is clearly detected in V, 
somewhat north of a source also seen in Pan-STARRS and in SDSS.

We find the afterglow to be V = 22.43 +/- 0.15 mag (AB mag, derived from 
two SDSS field stars transformed to V via the equations of Lupton 2005) 
at 0.43868 days after the GRB.


GRB_name: GRB210827A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30732
SUBJECT: GRB 210827A: Swift/BAT-GUANO detection and arcminute localization
DATE:    21/08/27 21:41:58 GMT
FROM:    Aaron Tohuvavohu at U Toronto  <aaron.tohu@gmail.com>

James DeLaunay (PSU), Gayathri Raman (PSU), Jamie A. Kennea (PSU),
Aaron Tohuvavohu (U Toronto),  report:

Swift/BAT did not trigger on GRB 210827A (T0: 2021-08-27 09:59:24.34
UTC, Fermi/GBM trigger #  651751169, GCN 30724).

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 duration of approximately 10 seconds.
Using the normal BAT imaging technique, we find the location for
the GRB with an SNR of 8.3.

The BAT position is
RA, Dec = 174.9181 +55.7858 deg which is
   RA(J2000)  = 11h 39m 40.34s
   Dec(J2000) =  +55d 47â€² 08.88â€³
with an estimated uncertainty of 4 arcmin.

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/


