# GCN_circulars

GRB_name: GRB240418A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36165
SUBJECT: GRB 240418A: AKO Upper Limit
DATE:    24/04/18 21:54:58 GMT
FROM:    Mohammad Odeh at Al Khatim Observatory M44 <mshodeh@gmail.com>

Mohammad Odeh (Al-Khatim Observatory, AKO, operated by the International
Astronomical Center in Abu Dhabi, UAE) and Nidhal Guessoum (American
University of Sharjah, UAE), report:

We observed the field of GRB 240418A (Siegel et al., GCN 36162) with our
0.36m f/7.7 robotic telescope.

We obtained 13x180s images using Ic filter on 18 April 2024, starting at
21:06UT, 42 minutes after the GRB trigger.

We did not detect any credible afterglow candidate within the updated XRT
position (Trigger number 1222885), down to the magnitude = 20.0 for the
stacked images.

The magnitude was estimated using the Atlas catalogue as a reference, and
it is not corrected for galactic extinction.


GRB_name: GRB240418A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36166
SUBJECT: GRB 240418A: Enhanced Swift-XRT position
DATE:    24/04/19 00:11:49 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.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 463 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 240418A, 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 = 239.37529, +23.59582 which is equivalent
to:

RA (J2000): 15h 57m 30.07s
Dec (J2000): +23d 35' 45.0"

with an uncertainty of 3.6 arcsec (radius, 90% confidence).

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

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


GRB_name: GRB240418A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36167
SUBJECT: GRB 240418A: NOT optical upper limits
DATE:    24/04/19 00:50:40 GMT
FROM:    Daniele B. Malesani at IMAPP / Radboud University <d.malesani@astro.ru.nl>

D. B. Malesani (DAWN/NBI and Radboud Univ.) and A. C. Casasbuenas (Univ. La Laguna and NOT) report on behalf of a larger collaboration.

We have observed the field of GRB 240418A (Siegel et al., GCN 36162) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were carried out under poor sky transparency, and consisted of images in the SDSS r and z bands (mean epochs 3.19 and 3.37 hr after trigger, respectively).

Within or close to the localization error circle of the X-ray afterglow (Evans et al., GCN 36166), we detect no object in either filter, down to limiting AB magnitudes r > 22, z > 20.4, calibrated against nearby stars from the Pan-STARRS catalog.


GRB_name: GRB240418A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36168
SUBJECT: GRB 240418A: TSHAO Zeiss-1000 optical upper limit
DATE:    24/04/19 01:36:41 GMT
FROM:    Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>

A. Pozanenko (IKI), I. Reva (FAI),  N.Pankov (HSE), S. Belkin (IKI)  report on behalf of GRB-IKI-FuN:

We have observed the field of GRB 240418A (Siegel et al., GCN 36162)  with Zeiss-1000 telescope of Tien Shan Astronomical Observatory starting on 2024-04-18 (UT) 21:47:25.

We do not detect  any object within Enhanced Swift-XRT position (Evans et al., GCN 36166) up to R=21.6. Preliminary photometry of the field in a stacked image is following.

Date       UT start t-T0    Filter  Exp.   OT  Err. UL(3 sigma)
                     (mid, days)     (s)
2024-04-18 21:47:25  -      R       21*120 n/d n/d  21.6

The photometry is based on nearby USNO-B1.0 stars.
Non detection of the OT is in agreement with the observations (Lipunov et al., GCN 36163; Odeh et al., GCN 36165; Malesani et al., GCN 36167).


GRB_name: GRB240419A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36169
SUBJECT: GRB 240419A: Swift detection of a burst
DATE:    24/04/19 02:03:17 GMT
FROM:    Simone Dichiara at Pennsylvania State University <sbd5667@psu.edu>


M. H. Siegel (PSU), S. Dichiara (PSU), R. Gupta (NASA/GSFC),
J. A. Kennea (PSU), S. Laha (GSFC/UMBC), D. M. Palmer (LANL) and
M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 01:48:01 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 240419A (trigger=1222955).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 94.568, -45.011 which is 
   RA(J2000) = 06h 18m 16s
   Dec(J2000) = -45d 00' 40"
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 4 sec.  The peak count rate
was ~1500 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 01:49:51.1 UT, 110.1 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source located at RA, Dec 94.53468, -45.00073 which
is equivalent to:
   RA(J2000)  = 06h 18m 08.32s
   Dec(J2000) = -45d 00' 02.6"
with an uncertainty of 3.5 arcseconds (radius, 90% containment). This
location is 92 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 consistent with the Galactic value of 6.63
x 10^20 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 113 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
0.069. 

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


GRB_name: GRB240419A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36170
SUBJECT: GRB 240419A: Prompt enhanced Swift-XRT position
DATE:    24/04/19 02:37:35 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.ac.uk>

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

Using  promptly downlinked XRT event data for GRB 240419A, we find an
enhanced XRT position of the afterglow: RA, Dec: 94.53358, -44.99999
which is equivalent to:
   RA (J2000)  = 06 18 08.06
   Dec (J2000) = -44 59 60.0
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/1222955.

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: GRB240419A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36174
SUBJECT: GRB 240419A: Enhanced Swift-XRT position
DATE:    24/04/19 08:08:55 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.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 977 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 240419A, 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 = 94.53406, -44.99952 which is equivalent
to:

RA (J2000): 06h 18m 8.17s
Dec (J2000): -44d 59' 58.3"

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: GRB240419A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36175
SUBJECT: GRB 240419A: VLT optical afterglow detection
DATE:    24/04/19 08:17:24 GMT
FROM:    Daniele B. Malesani at IMAPP / Radboud University <d.malesani@astro.ru.nl>

B. Schneider (MIT), N. Gaspari (Radboud Univ.), N. R. Tanvir (Univ. Leicester), S. Covino (INAF/Brera), D. B. Malesani (DAWN/NBI and Radboud Univ.), L. Izzo (INAF/Napoli and DARK/NBI), A. Saccardi (GEPI/Obs. Paris), report on behalf of the Stargate collaboration.

We observed the field of GRB 240419A (Siegel et al., GCN 36169) using the ESO VLT UT1 equipped with the FORS2 camera. Observations were commenced automatically in rapid-response mode (RRM). The first image was acquired on April 19.0895 UT, that is, 20.9 min after the GRB, and consisted of a 20 s image in the R filter. At a relatively high airmass of 2.1, the delivered PSF was 1.4".

A source, not present in archival images, is detected within the UVOT-enhanced XRT error circle (Goad et al., GCN 36174), at coordinates (J2000):

RA = 06:18:08.17
Dec = -44:59:57.3

Using FORS2 zeropoints, we measure for the source a magnitude R = 19.88 +- 0.05 (Vega), in excellent agreement with photometry calibrated against nearby stars from the SkyMapper catalog.

Further observations have been secured and will be reported at a later time. We acknowledge excellent support from the ESO observing staff in Paranal.


GRB_name: GRB240418A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36177
SUBJECT: GRB240418A: YAHPT Upper Limits
DATE:    24/04/19 11:15:10 GMT
FROM:    Tianrui Sun at Purple Mountain Obs,CAS <trsun@pmo.ac.cn>

Tian-Rui Sun, Jin-Jun Geng, Jian Chen, Yan-Long Hua  and Lei Hu report on behalf of the YAHPT team:

Following the detection of GRB 240418A by SWIFT (Siegel et al., GCN 36162; Evans et al., GCN 36166), 
we use the Yaoan High Precision Telescope at Yaoan Astronomy Observation Station (Yunnan province, China) to search and follow up its afterglow at XRT position.

We observed the target position with 180s exposure in V-band starting from 2024-04-18T20:32:14.600 about 486.6 seconds after the burst.
We took 25 images with total exposure time of 4500 seconds from 20:32:14 to 21:48:29.4. 
We did not detect any object up to V = 22.2 with the stacked images within the Enhanced Swift XRT position 
This non-detection results of the gamma-ray bursts is in agreement with the previous circulars 
(Lipunov et al., GCN 36163; Odeh et al., GCN 36165; Malesani et al., GCN 36167; Pozanenko et al. GCN 36168;).

We used the UCAC4 catalog (Vmag) as the magnitude reference for calibration.


GRB_name: GRB240411B
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36179
SUBJECT: GRB 240411B: Swift/UVOT Detection
DATE:    24/04/19 12:32:47 GMT
FROM:    Sam LaPorte at PSU <sjl5346@psu.edu>

S. J. LaPorte (PSU) and T. M. Parsotan (GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 240411B
190 s after the BAT trigger (Parsotan et al., GCN Circ. 36063). A source
consistent
with the XRT position (Goad et al., GCN Circ. 36065) and the reported
optical transient (Izzo et al. GCN 36064; Schneider et
al. GCN 36067; Ror et al. GCN 36069; Ugarte Postigo et al. GCN 36074; Aryan
et al. GCN 36077; Pankov et al. GCN 36078) 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

b                      6480          6680           196        >19.84
v                      7096          7295           196        >18.58
uvw2                6891          7091           196        >19.45
white                6685          6885           196        >20.54
white                 198            348           147           20.08+-0.27


The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.022 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB240419B
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36180
SUBJECT: GRB 240419B: Swift detection of a burst
DATE:    24/04/19 12:43:36 GMT
FROM:    Jamie Kennea at Penn State <jak51@psu.edu>


S. Dichiara (PSU), J.D. Gropp (PSU), R. Gupta (NASA/GSFC),
F. E. Marshall (NASA/GSFC), M. J. Moss (GSFC),
P. T. O'Brien (U Leicester), M. H. Siegel (PSU) and
M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 12:22:52 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 240419B (trigger=1223072).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 325.877, +4.234 which is 
   RA(J2000) = 21h 43m 30s
   Dec(J2000) = +04d 14' 01"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex structure lasted 
for ~40 seconds and returned to background before showing three bright pulses at 
~100 seconds for a total duration of 160 seconds.  The peak count rate
was ~2049 counts/sec (15-350 keV), at ~119 sec after the trigger. 

The XRT began observing the field at 12:25:20.7 UT, 148.4 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 325.89615, 4.23548 which
is equivalent to:
   RA(J2000)  = 21h 43m 35.08s
   Dec(J2000) = +04d 14' 07.7"
with an uncertainty of 3.5 arcseconds (radius, 90% containment). This
location is 68 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 consistent with the Galactic value of 6.84
x 10^20 cm^-2 (Willingale et al. 2013). 

The initial flux in the 2.5 s image was 7.01e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 158 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
0.077. 

Burst Advocate for this burst is S. Dichiara (sbd5667 AT psu.edu). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB240418A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36181
SUBJECT: GRB 240418A: Swift-XRT refined Analysis
DATE:    24/04/19 15:17:47 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.ac.uk>

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

We have analysed 6.1 ks of XRT data for GRB 240418A, from 107 s to 44.9
ks after the  BAT trigger. The data comprise 7 s in Windowed Timing
(WT) mode (taken while Swift was slewing), with the remainder in Photon
Counting (PC) mode. 

The light curve can be modelled with a power-law decay with a decay
index of alpha=2.9 (+0.3, -0.4).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.0 (+0.6, -0.4). The
best-fitting absorption column is  consistent with the Galactic value
of 5.3 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 3.2 x 10^-11 (3.5 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      5 (+/-12) x 10^20 cm^-2
Galactic foreground: 5.3 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:      2.0 (+0.6, -0.4)

If the light curve continues to decay with a power-law decay index of
2.9, the count rate at T+24 hours will be 1.2 x 10^-8 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.8 x
10^-19 (4.1 x 10^-19) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01222885.

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


GRB_name: GRB240419A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36182
SUBJECT: GRB 240419A: Swift-XRT refined Analysis
DATE:    24/04/19 15:20:33 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.ac.uk>

A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), M. Perri
(SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti
(INAF-OAB), D.N. Burrows (PSU), J. D. Gropp (PSU), S. Dichiara (PSU)
and P.A. Evans report on behalf of the Swift-XRT team:

We have analysed 7.8 ks of XRT data for GRB 240419A, from 117 s to 33.6
ks after the  BAT trigger. The data are entirely in Photon Counting
(PC) mode. 

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=5.3 (+2.7, -0.8). At T+249 s  the decay
flattens to an alpha of -0.2 (+0.7, -0.6) before breaking again at
T+1406 s to a final decay with index alpha=1.20 (+0.32, -0.25).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.30 (+0.30, -0.27). The
best-fitting absorption column is  2.4 (+1.1, -0.9) x 10^21 cm^-2, in
excess of the Galactic value of 6.6 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 3.1 x 10^-11 (5.1 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      2.4 (+1.1, -0.9) x 10^21 cm^-2
Galactic foreground: 6.6 x 10^20 cm^-2
Excess significance: 3.1 sigma
Photon index:      2.30 (+0.30, -0.27)

If the light curve continues to decay with a power-law decay index of
1.20, the count rate at T+24 hours will be 2.8 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.7 x
10^-14 (1.4 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01222955.

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


GRB_name: GRB240419A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36183
SUBJECT: GRB 240419A: REM NIR afterglow detection
DATE:    24/04/19 15:36:10 GMT
FROM:    Matteo Ferro at INAF-OAB <matteo.ferro@inaf.it>

M. Ferro, Y.-D. Hu, P. Dâ€™Avanzo, R. Brivio, S. Covino, D. Fugazza (INAF-OAB) on behalf of the REM team, report:

We observed for the field of GRB 240419A (Siegel et al., GCN 36169) with the REM 60cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, K bands, starting on 2024 April 19 at 01:49:38 UT (i.e. 1.6 minutes after the event), and lasting for about 3 hours.
From preliminary photometry we detect the  NIR afterglow at a position consistent with the optical afterglow position (Schneider et al., GCN 36175), at the following AB magnitude in the H band:

H = 15.7 +- 0.1 (calibrated against 2MASS catalogue)
at a mid time of t-t0 ~ 4 minutes after the GRB trigger.

The afterglow is not detected in our optical observations, at the following AB magnitude limit in the r band:

r > 19.2 (calibrated against SkyMapper catalogue)
at a mid time of t-t0 ~ 6.3 minutes after the GRB trigger.


GRB_name: GRB240418A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36184
SUBJECT: GRB 240418A: Swift/UVOT Upper Limits
DATE:    24/04/19 16:06:19 GMT
FROM:    Sam Shilling at Lancaster University <shilling.sam@gmail.com>

S. P. R. Shilling (Lancaster U.), S. R. Oates (Lancaster U.),  A. A. Breeveld (UCL-MSSL),  N. P. M. Kuin (UCL-MSSL) and M. H. Siegel (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 240418A
126 s after the BAT trigger (Siegel et al., GCN Circ. 36162).
No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 36166)
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           126          276          147         >20.6
u_FC               284          533          246         >19.4
white              126         5282          347         >21.1
v                 4072         4272          197         >19.3
b                  539         5093          216         >20.2
u                  284         4888          442         >19.9
w1                4482         4682          197         >19.7
m2                4276         4476          197         >19.5

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.057 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB240419A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36185
SUBJECT: Swift GRB 240419A: Global MASTER-Net observations report
DATE:    24/04/19 17:03:54 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>

V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik,  D. Vlasenko,
G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij
(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. Gress, N.M. Budnev, O.Ershova
(Irkutsk State University, API),

L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez
(INAOE, Guillermo Haro Astrophysics Observatory),

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

V. Yurkov, A. Gabovich
(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 240419A ( M. H. Siegel et al., GCN 36169) errorbox  54337 sec after notice time and 54397 sec after trigger time at 2024-04-19 16:54:39 UT, with upper limit up to  17.8 mag. Observations started at twilight.  The observations began at zenith distance = 25 deg. The sun  altitude  is -9.6 deg. 

The galactic latitude b = -24 deg., longitude l = 253 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2427118

We obtain a following upper limits.  

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

   54488 |         MASTER-SAAO |   C |   180 | 17.8 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB240419B
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36186
SUBJECT: GRB 240419B: Enhanced Swift-XRT position
DATE:    24/04/19 17:38:53 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.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 1231 s of XRT Photon Counting mode data and 3 UVOT
images for GRB 240419B, 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 = 325.89679, +4.23479 which is equivalent
to:

RA (J2000): 21h 43m 35.23s
Dec (J2000): +04d 14' 05.2"

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: GRB240419B
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36188
SUBJECT: Swift GRB 240419B: Global MASTER-Net observations report
DATE:    24/04/19 19:36:52 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>

V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik,  D. Vlasenko,
G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij
(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. Gress, N.M. Budnev, O.Ershova
(Irkutsk State University, API),

L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez
(INAOE, Guillermo Haro Astrophysics Observatory),

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

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

MASTER-Amur robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Blagoveshchensk State Pedagogical University) was pointed to the Swift GRB 240419B ( S. Dichiara et al., GCN 36180) errorbox  24752 sec after notice time and 24919 sec after trigger time at 2024-04-19 19:18:11 UT, with upper limit up to  15.6 mag. Observations started at twilight.  The observations began at zenith distance = 69 deg. The sun  altitude  is -11.0 deg. 

The galactic latitude b = -35 deg., longitude l = 61 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2427564

We obtain a following upper limits.  

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

   25009 |         MASTER-Amur |   C |   180 | 15.1 |        
   25009 |         MASTER-Amur |   C |   180 | 15.6 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB240419B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36191
SUBJECT: GRB 240419B: optical afterglow from the NOT
DATE:    24/04/20 06:40:47 GMT
FROM:    Daniele B. Malesani at IMAPP / Radboud University <d.malesani@astro.ru.nl>

Daniele B. Malesani (DAWN/NBI and Radboud Univ.) and David Jones (NOT) report on behalf of a larger collaboration.

We observed the field of GRB 240419B (Dichiara et al., GCN 36180) with the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were carried out straddling the morning twilight, at airmass ~2, and the seeing was about 1.7".

An object consistent with the X-ray localization error circle (Osborne et al., GCN 36186) is detected in our images. Its coordinates are (J2000):

RA = 21:43:35.289
Dec = +04:14:05.30

Calibrating against nearby point-like sources from the Pan-STARRS catalog, we measure the following AB magnitudes:

r = 22.01 +- 0.10  (Apr 20.214 UT, or 0.698 days after the trigger);
z = 20.81 +- 0.19  (Apr 20.222 UT, or 0.701 days after the trigger).

This object is not visible in the Legacy Survey images, which are deeper than ours, and we thus conclude that it is the optical afterglow of GRB 240419B. We note however the presence of a fainter (r ~ 23.2), distinct source visible in the Legacy Survey, approximately 2.5" to the west of the afterglow. Given the relatively large offset, the relation of this object with the GRB is unclear.


GRB_name: GRB240419B
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36192
SUBJECT: GRB 240419B: Swift-XRT refined Analysis
DATE:    24/04/20 08:11:17 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.ac.uk>

J.P. Osborne (U. Leicester), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti
(INAF-OAB), C. Salvaggio (INAF-OAB), J. D. Gropp (PSU), S. Dichiara
(PSU), J.A. Kennea (PSU), K.L. Page (U. Leicester) and P.A. Evans
report on behalf of the Swift-XRT team:

We have analysed 7.5 ks of XRT data for GRB 240419B, from 141 s to 52.1
ks after the  BAT trigger. The data comprise 282 s in Windowed Timing
(WT) mode (the first 6 s were taken while Swift was slewing) with the
remainder in Photon Counting (PC) mode. 

The late-time light curve (from T0+4.6 ks) can be modelled with a
power-law decay with a decay index of alpha=1.02 (+0.12, -0.11).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.95 (+/-0.05). The
best-fitting absorption column is  1.21 (+0.16, -0.15) x 10^21 cm^-2,
in excess of the Galactic value of 6.8 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.08 (+0.20, -0.19)
and a best-fitting absorption column of 1.2 (+/-0.5) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.2 x 10^-11 (4.2 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.2 (+/-0.5) x 10^21 cm^-2
Galactic foreground: 6.8 x 10^20 cm^-2
Excess significance: 1.7 sigma
Photon index:      2.08 (+0.20, -0.19)

If the light curve continues to decay with a power-law decay index of
1.02, the count rate at T+24 hours will be 10.0 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.2 x
10^-13 (4.2 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/01223072.

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


GRB_name: GRB240419B
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36197
SUBJECT: GRB 240419B: Swift/UVOT Upper Limits
DATE:    24/04/20 15:20:59 GMT
FROM:    Sam Shilling at Lancaster University <shilling.sam@gmail.com>

S. P. R. Shilling (Lancaster U.), S. R. Oates (Lancaster U.),
A. A. Breeveld (UCL-MSSL), N. P. M. Kuin (UCL-MSSL) and S. Dichiara (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 240419B
159 s after the BAT trigger (Dichiara et al., GCN Circ. 36180).
No optical afterglow consistent with either the enhanced XRT position
(Osborne et al., GCN Circ. 36186) or the NOT optical afterglow position
(Malesani et al., GCN Circ. 36191) 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) exposures and subsequent exposures are:

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

white_FC           159          308          147         >20.3
u_FC               317          567          246         >19.5
white              159          790          186         >20.4
v                  647          667           19         >17.3
b                  572          765           39         >18.6
u                  317          741          265         >19.5
w1                 696          716           19         >17.5
m2                 672          691           19         >17.2
w2                 623          643           19         >17.6

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.077 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB240418A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36199
SUBJECT: GRB240418A - Candidate afterglow from NIRES
DATE:    24/04/20 19:35:35 GMT
FROM:    Viraj Karambelkar at Indian Inst of Tech,Bombay <karambelkarvraj21197@gmail.com>

Viraj Karambelkar (Caltech), Kaew Tinyanont (NARIT), Sam Rose (Caltech),
Tomas Ahumada (Caltech), Robert Stein (Caltech), Nathan Lourie (MIT),
Danielle Frostig (MIT), Geoffrey Mo (MIT), Robert Simcoe (MIT), Mansi
Kasliwal (Caltech)

We observed the field of the long GRB 240418A (GCN 36162; GCN 36166; GCN
36177; GCN 36184) in the near-infrared K-prime band with the NIRES
acquisition camera on the Keck II telescope starting at UTC
2024-04-19T09:56:00 (~14 hours since trigger). The observations lasted for
300 sec. (25 sec, 12 coadds).

We find an uncataloged source at RA = 239.3744, Dec = 23.5961 that is 3.1
arcsec from the centroid of the GRB position and within its 3.6 arcsec
localization (from GCN 36166). This source has m_Kp ~ 20.9 +/- 0.1 mag
(AB). There is no source at this location in an archival Ks-band image from
the UKIRT hemisphere survey (Lucas et al. 2008), and a deep optical image
from the Legacy Survey. However, we note that our NIRES observations are
more sensitive than the archival UKIRT observations, so it is possible that
the NIRES source is an unrelated background source.

We also observed this source in the J-band with the WINTER camera on the
Palomar 40-inch telescope (Lourie et al. 2021) on 2024-04-19T09:00:14 and
did not detect it to a limiting magnitude of m_J ~ 19 mag.

Further observations are encouraged.


GRB_name: GRB240419A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36200
SUBJECT: GRB240419A: Skynet Optical Afterglow Analysis
DATE:    24/04/20 21:12:37 GMT
FROM:    maedubay@unc.edu

Megan Dubay, Donovan Schlekat, Dylan Dutton, Daniel Reichart, Joshua Haislip, and Vladimir Kouprianov report on behalf of the Skynet Robotic Telescope Network at the University of North Carolina at Chapel Hill.

We observed the field of GRB 240419A with one of Skynetâ€™s 16â€-diameter PROMPT telescopes at CTIO. The first detection occurred in the I band approximately 1 hour after the trigger reported by Swift (Siegel et al., GCN 36169).

We detect the afterglow with coordinates consistent with those reported by VLT (B. Schneider et al., GCN 36175) and REM (Ferro et al., GCN 36183).

The coordinates are: 
R.A. (J2000):  06:18:08.18
Dec. (J2000): -44:59:57.60

We report the photometry below.

ExpLen | Filter | Mag   | Mag Error  | MJD (Center)   
------------------------------------------------
45x8   | I      | 19.06 | 0.199      | 60419.119
60x8   | R      | ----- | -----      | 60419.119

We report non-detection in the R-band from the reported time with an upper magnitude limit of 20.39.
 
We note that the large R-I color is consistent with the presence of the Lyman-alpha forest in the R band, given its large redshift (Schneider et al., GCN 36176, Lamb & Reichart 2000).

Our images have been calibrated using stars from the APASS catalog.


GRB_name: GRB240421A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36204
SUBJECT: GRB 240421A: Fermi GBM Final Real-time Localization
DATE:    24/04/21 05:32:35 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 05:21:59 UT on 21 Apr 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240421A (trigger 735369724.901026 / 240421224).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 314.2, Dec = -80.2 (J2000 degrees, equivalent to J2000 20h 56m, -80d 12'), with a statistical uncertainty of 7.5 degrees.

The angle from the Fermi LAT boresight is 140.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240421224/quicklook/glg_skymap_all_bn240421224.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240421224/quicklook/glg_healpix_all_bn240421224.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240421224/quicklook/glg_lc_medres34_bn240421224.gif


GRB_name: GRB240421B
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36208
SUBJECT: GRB 240421B: Swift detection of a burst
DATE:    24/04/21 10:02:18 GMT
FROM:    Simone Dichiara at Pennsylvania State University <sbd5667@psu.edu>


M. A. Williams (PSU), J. J. DeLaunay (PSU), S. Dichiara (PSU),
J.D. Gropp (PSU) and T. Sakamoto (AGU) report on behalf of the Neil
Gehrels Swift Observatory Team:

At 09:42:54 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 240421B (trigger=1223470).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 299.686, -14.879 which is 
   RA(J2000) = 19h 58m 45s
   Dec(J2000) = -14d 52' 42"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multi-peaked
structure with a duration of about 20 sec.  The peak count rate
was ~9000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 09:45:00.4 UT, 126.3 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 299.70011, -14.86012
which is equivalent to:
   RA(J2000)  = 19h 58m 48.03s
   Dec(J2000) = -14d 51' 36.4"
with an uncertainty of 1.9 arcseconds (radius, 90% containment). This
location is 83 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 (1.24 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 3.8
(+2.62/-2.25) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 129 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
0.183. 

Burst Advocate for this burst is M. A. Williams (mjw6837 AT psu.edu). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB240421A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36212
SUBJECT: Fermi GRB 240421A: Global MASTER-Net observations report
DATE:    24/04/21 18:16:47 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>

V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik,  D. Vlasenko,
G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij
(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. Gress, N.M. Budnev, O.Ershova
(Irkutsk State University, API),

L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez
(INAOE, Guillermo Haro Astrophysics Observatory),

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

V. Yurkov, A. Gabovich
(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 240421A ( Fermi GBM team, GCN 36204) errorbox  42622 sec after notice time and 42658 sec after trigger time at 2024-04-21 17:12:58 UT, with upper limit up to  16.7 mag. Observations started at twilight.  The observations began at zenith distance = 66 deg. The sun  altitude  is -13.9 deg. 

The galactic latitude b = -32 deg., longitude l = 313 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2430011

We obtain a following upper limits.  

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

   42689 | 2024-04-21 17:12:58 |         MASTER-SAAO | (20h 50m 46.74s , -82d 18m 27.9s) |   C |    60 | 14.2 |        
   42689 | 2024-04-21 17:12:58 |         MASTER-SAAO | (21h 03m 23.96s , -82d 31m 37.4s) |   C |    60 | 14.4 |        
   42768 | 2024-04-21 17:14:18 |         MASTER-SAAO | (20h 29m 07.64s , -78d 43m 31.0s) |   C |    60 | 14.5 |        
   42768 | 2024-04-21 17:14:18 |         MASTER-SAAO | (20h 20m 41.90s , -78d 30m 17.8s) |   C |    60 | 14.2 |        
   43087 | 2024-04-21 17:19:37 |         MASTER-SAAO | (20h 24m 07.82s , -84d 24m 28.5s) |   C |    60 | 16.7 |        
   43087 | 2024-04-21 17:19:37 |         MASTER-SAAO | (20h 07m 14.94s , -84d 11m 11.3s) |   C |    60 | 16.6 |        
   43167 | 2024-04-21 17:20:56 |         MASTER-SAAO | (19h 08m 34.69s , -82d 29m 18.5s) |   C |    60 | 15.9 |        
   43167 | 2024-04-21 17:20:56 |         MASTER-SAAO | (18h 55m 46.97s , -82d 15m 59.6s) |   C |    60 | 15.8 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB240421B
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36213
SUBJECT: GRB 240421B: Enhanced Swift-XRT position
DATE:    24/04/21 18:31:11 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.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 1017 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 240421B, 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 = 299.70085, -14.85962 which is equivalent
to:

RA (J2000): 19h 58m 48.20s
Dec (J2000): -14d 51' 34.6"

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: GRB240421B
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36214
SUBJECT: GRB 240421B: Swift/UVOT Upper Limits
DATE:    24/04/21 19:04:49 GMT
FROM:    Paul Kuin at MSSL <npkuin@gmail.com>

N. P. M. Kuin (UCL-MSSL) and M. Williams (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 240421B
130s after the BAT trigger (Williams et al., GCN Circ. 36208).  No
optical afterglow consistent with the XRT position Beardmore et al.
(GCN Circ. 36213) 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           130          279          148         >20.6
u_FC               343          592          246         >20.2
white              130         1708          218         >20.9
v                  672         1764           78         >18.4
b                  598         1854           84         >19.8
u                  343         1827          339         >20.2
w1                 721         1813           78         >19.4
w2                 648         1568           78         >18.8

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.182 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB240421B
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36215
SUBJECT: GRB 240421B: J-band upper limits from WINTER
DATE:    24/04/21 19:08:39 GMT
FROM:    Viraj Karambelkar at Indian Inst of Tech,Bombay <karambelkarvraj21197@gmail.com>

Viraj Karambelkar (Caltech), Geoffrey Mo (MIT), Robert Stein (Caltech),
Danielle Frostig (MIT), Tomas Ahumada (Caltech), Nathan Lourie (MIT),
Robert Simcoe (MIT), Mansi Kasliwal (Caltech)

We observed the field of the long GRB 240421B (GCN 36208, 36213, 36214) in
the near-IR J-band with the WINTER camera on the Palomar 40-inch telescope.
Our observations started at UTC 2024-04-19T11:16:00 (~1.5 hours since
trigger) and lasted for an hour.

The images were processed through the WINTER data reduction pipeline
implemented using mirar (https://zenodo.org/records/10888437), with image
subtraction performed relative to reference images built from the VISTA
Hemisphere Survey (McMahon et al. 2013).



We do not detect any source at the location of the X-ray counterpart
(reported in GCN 36213) to a limit of m_J = 19.5 mag (AB, not corrected for
Galactic extinction). No other new sources are found within the 3 arcmin
localization of the GRB.

WINTER (Wide-field INfrared Transient ExploreR) is a partnership between
MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF
AAG, the David and Lucille Packard Foundation, and the MIT Kavli Institute
for Astrophysics and Space Research


GRB_name: GRB240421B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36216
SUBJECT: GRB240421B: BOOTES-5/JGT optical upper limit
DATE:    24/04/21 21:10:58 GMT
FROM:    Youdong HU at INAF-OAB <huyoudong072@hotmail.com>

E. Fernandez-Garcia, I. Perez-Garcia, M.D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy, S.-Y. Wu and A. J. Castro-Tirado (IAA-CSIC, Granada), Y.-D. Hu (INAF-OAB), P. J. Meintjes and H. J. van Heerden (UFS, South Africa), A. Martin-Carrillo and L. Hanlon (UCD, Ireland) and C. J. Perez del Pulgar (UMA, Malaga), on behalf of a larger collaboration, report:

Following the detection of GRB 240421B by Swift (Williams et al. GCNC 36208), the BOOTES-5/JGT 0.6m robotic telescope at Observatorio Astronomico Nacional in San Pedro Martir (Mexico) automatically observed the GRB location starting on April. 21, 09:43:44 UT (~ 50 s after trigger). No new optical source is detected on the co-added images (20 x 1 s, clear-filter) within the enhanced Swift/XRT error box (Beardmore et al. GCNC 36213) down to 18.4 mag.  which is consistent with both reports from UVOT (Kuin et al., GCNC 36214) and WINTER (Karambelkar et al. GCNC 36215).

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


GRB_name: GRB240421B
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36217
SUBJECT: GRB 240421B: Swift-XRT refined Analysis
DATE:    24/04/21 22:50:00 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.ac.uk>

J.P. Osborne (U. Leicester), B. Sbarufatti (INAF-OAB), C. Salvaggio
(INAF-OAB), M. Ferro (INAF-OAB), S. Dichiara (PSU), J.A. Kennea (PSU),
A. Tohuvavohu (U. Toronto), K.L. Page (U. Leicester), A.P. Beardmore
(U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team:

We have analysed 6.6 ks of XRT data for GRB 240421B, from 110 s to 36.0
ks after the  BAT trigger. The data comprise 42 s in Windowed Timing
(WT) mode (the first 9 s were taken while Swift was slewing) with the
remainder in Photon Counting (PC) mode. 

The light curve can be modelled with an initial power-law decay with an
index of alpha=0.50 (+/-0.07), followed by a break at T+2500 s to an
alpha of 1.20 (+/-0.10).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.87 (+/-0.13). The
best-fitting absorption column is  6.5 (+1.0, -0.9) x 10^21 cm^-2, in
excess of the Galactic value of 1.2 x 10^21 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 4.6 x 10^-11 (7.3 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      6.5 (+1.0, -0.9) x 10^21 cm^-2
Galactic foreground: 1.2 x 10^21 cm^-2
Excess significance: 9.6 sigma
Photon index:      1.87 (+/-0.13)

If the light curve continues to decay with a power-law decay index of
1.20, the count rate at T+24 hours will be 0.023 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x
10^-12 (1.7 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/01223470.

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


GRB_name: GRB240421B
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36218
SUBJECT: GRB 240421B: Fermi GBM Observation
DATE:    24/04/21 23:05:42 GMT
FROM:    Cori Fletcher at USRA <cfletcher@usra.edu>

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

"At 09:42:41.91 UT on 21 April 2024, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 240421B (trigger 735385366/240421405).
which was also detected by Swift BAT (M. A. Williams et al. 2024, GCN 36208).
The Fermi GBM on-ground location is consistent with the Swift BAT position.

The angle from the Fermi LAT boresight is 29 degrees.

The GBM light curve consists of multiple peaks with a duration (T90)
of about 12.3 s (50-300 keV). The time-averaged spectrum
from T0+0.003 to T0+18.4 s is best fit by
a Band function with Epeak = 141 +/- 8 keV,
alpha = -0.91 +/- 0.04, and beta = -2.31 +/- 0.09.

The event fluence (10-1000 keV) in this time interval is
(1.28 +/- 0.02)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+12 s in the 10-1000 keV band is 31.9 +/- 0.5 ph/s/cm^2.

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

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


GRB_name: GRB240421B
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36219
SUBJECT: Swift GRB 240421B: Global MASTER-Net observations report
DATE:    24/04/22 00:24:46 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>

V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik,  D. Vlasenko,
G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij
(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. Gress, N.M. Budnev, O.Ershova
(Irkutsk State University, API),

L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez
(INAOE, Guillermo Haro Astrophysics Observatory),

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

V. Yurkov, A. Gabovich
(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 240421B ( M. A. Williams et al., GCN 36208) errorbox  52346 sec after notice time and 52368 sec after trigger time at 2024-04-22 00:15:42 UT, with upper limit up to  16.5 mag. The observations began at zenith distance = 70 deg. The sun  altitude  is -20.3 deg. 

The galactic latitude b = -22 deg., longitude l = 27 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2430219

We obtain a following upper limits.  

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

   52459 |   MASTER-Kislovodsk |   C |   180 | 15.8 |        
   52459 |   MASTER-Kislovodsk |   C |   180 | 16.5 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB240421B
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36220
SUBJECT: Fermi GRB 240421B: Global MASTER-Net observations report
DATE:    24/04/22 02:15:40 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>

V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik,  D. Vlasenko,
G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij
(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. Gress, N.M. Budnev, O.Ershova
(Irkutsk State University, API),

L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez
(INAOE, Guillermo Haro Astrophysics Observatory),

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

V. Yurkov, A. Gabovich
(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 240421B ( C. Fletcher (USRA) and C. Meegan (UAH) report on behalf of et al., GCN 36218) errorbox  19358 sec after notice time and 56607 sec after trigger time at 2024-04-22 01:26:08 UT, with upper limit up to  17.1 mag. Observations started at twilight.  The observations began at zenith distance = 67 deg. The sun  altitude  is -14.1 deg. 

The galactic latitude b = -22 deg., longitude l = 22 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2430649

We obtain a following upper limits.  

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

   56637 | 2024-04-22 01:26:08 |      MASTER-Tavrida | (19h 37m 21.45s , -18d 16m 09.9s) |   C |    60 | 16.4 |        
   56785 | 2024-04-22 01:28:36 |      MASTER-Tavrida | (19h 53m 26.05s , -18d 16m 57.8s) |   C |    60 | 14.1 |        
   56858 | 2024-04-22 01:29:50 |      MASTER-Tavrida | (19h 49m 21.85s , -22d 05m 18.0s) |   C |    60 | 14.2 |        
   57563 | 2024-04-22 01:41:35 |      MASTER-Tavrida | (19h 50m 44.40s , -20d 11m 20.7s) |   C |    60 | 15.8 |        
   57636 | 2024-04-22 01:42:47 |      MASTER-Tavrida | (19h 59m 17.11s , -20d 10m 02.0s) |   C |    60 | 16.6 |        
   57709 | 2024-04-22 01:44:00 |      MASTER-Tavrida | (19h 37m 21.08s , -18d 16m 19.0s) |   C |    60 | 17.1 |        
   57782 | 2024-04-22 01:45:13 |      MASTER-Tavrida | (19h 45m 45.17s , -18d 15m 26.6s) |   C |    60 | 17.0 |        
   57926 | 2024-04-22 01:47:38 |      MASTER-Tavrida | (19h 43m 02.18s , -20d 11m 33.0s) |   C |    60 | 16.8 |        
   57999 | 2024-04-22 01:48:50 |      MASTER-Tavrida | (19h 53m 25.96s , -18d 17m 25.9s) |   C |    60 | 16.7 |        
   58144 | 2024-04-22 01:51:16 |      MASTER-Tavrida | (19h 49m 20.84s , -22d 05m 40.1s) |   C |    60 | 14.5 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB240421B
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36221
SUBJECT: GRB240421B: Zadko Observations
DATE:    24/04/22 02:30:22 GMT
FROM:    Bruce Gendre at UWA <bruce.gendre@gmail.com>

B. Gendre, E. Moore, F. Panther, D. Coward, J. A. Moore (OzGrav-UWA),
and A. Klotz (IRAP-CNRS-OMP),
report:

We imaged the field of GRB 240421B detected by SWIFT
(trigger 1223470) with the Zadko robotic telescope (D=100cm)
located at the observatory - Gingin, Australia.

The observations started 7.97h after the GRB trigger.
The elevation of the field increased from
25 degrees above horizon and weather conditions
were good.

The date of trigger : t0 = 2024-04-21T09:42:54.050

The first image is 60.0s exposure in tracking mode:
t0+28754.8s to t0+28814.8s : R > 16.2

We co-added a series of exposures:
t0+28754.8s to t0+29599.3s : R > 17.7

Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.

N.B. Galactic coordinates are lon= 26.7039 lat=-21.4736
and the galactic extinction in R band is 0.7 magnitudes
estimated from D. Schlegel et al. 1998ApJ...500..525S.

This message may be cited.


GRB_name: GRB240422A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36222
SUBJECT: GRB 240422A: Fermi GBM Final Real-time Localization
DATE:    24/04/22 02:51:32 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 02:40:59 UT on 22 Apr 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240422A (trigger 735446464.467214 / 240422112).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 255.6, Dec = -67.4 (J2000 degrees, equivalent to J2000 17h 02m, -67d 24'), with a statistical uncertainty of 9.9 degrees.

The angle from the Fermi LAT boresight is 23.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240422112/quicklook/glg_skymap_all_bn240422112.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240422112/quicklook/glg_healpix_all_bn240422112.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240422112/quicklook/glg_lc_medres34_bn240422112.gif


GRB_name: GRB240421B
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36223
SUBJECT: GRB 240421B: AstroSat CZTI detection
DATE:    24/04/22 04:47:37 GMT
FROM:    Gaurav Waratkar at IIT Bombay <gauravwaratkar@iitb.ac.in>

G. Waratkar (IITB),  J. Joshi (IUCAA), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/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., 2021, JApA, 42, 73) showed the detection of a long-duration GRB 240421B which was also detected by Swift-BAT (Williams et al., GCN Circ. 36208) and Fermi-GBM (Fletcher et al., GCN Circ. 36218).

The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2024-04-21 09:42:54.5 UTC. The measured peak count rate associated with the burst is 368 (+44, -52) counts/s above the background in the combined data of all quadrants, with a total of 843 (+148, -223) counts. The local mean background count rate was 474 (+5, -4) counts/s. Using cumulative rates, we measure a T90 of 6.3 (+3.2, -2.7) s.

It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2024-04-21 09:42:53.8 UTC. The measured peak count rate is 745 (+82, -87) counts/s above the background in the combined Veto data of all quadrants, with a total of 1802 (+268, -278) counts. The local mean background count rate was 1740 (+7, -8) counts/s. We measure a T90 of 5.6 (+1.6, -1.7) s from the cumulative Veto light curve.

CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project.

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


GRB_name: GRB240422A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36224
SUBJECT: Fermi GRB 240422A: Global MASTER-Net observations report
DATE:    24/04/22 05:31:57 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>

V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik,  D. Vlasenko,
G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij
(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. Gress, N.M. Budnev, O.Ershova
(Irkutsk State University, API),

L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez
(INAOE, Guillermo Haro Astrophysics Observatory),

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

V. Yurkov, A. Gabovich
(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 240422A ( Fermi GBM team, GCN 36222) errorbox  2591 sec after notice time and 2626 sec after trigger time at 2024-04-22 03:24:46 UT, with upper limit up to  19.3 mag. The observations began at zenith distance = 45 deg. The sun  altitude  is -21.7 deg. 

The galactic latitude b = -16 deg., longitude l = 324 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2430987

We obtain a following upper limits.  

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

    2657 | 2024-04-22 03:24:46 |         MASTER-SAAO | (18h 35m 02.79s , -76d 43m 27.3s) |   C |    60 | 19.1 |        
    3878 | 2024-04-22 03:45:07 |         MASTER-SAAO | (18h 35m 34.85s , -76d 42m 39.4s) |   C |    60 | 18.0 |        
    4038 | 2024-04-22 03:47:47 |         MASTER-SAAO | (16h 59m 17.39s , -67d 19m 40.0s) |   C |    60 | 18.8 |        
    4038 | 2024-04-22 03:47:47 |         MASTER-SAAO | (16h 54m 35.38s , -67d 06m 21.1s) |   C |    60 | 19.1 |        
    4118 | 2024-04-22 03:49:07 |         MASTER-SAAO | (16h 57m 08.53s , -68d 58m 52.2s) |   C |    60 | 19.3 |        
    4118 | 2024-04-22 03:49:07 |         MASTER-SAAO | (17h 02m 14.07s , -69d 12m 12.4s) |   C |    60 | 19.1 |        
    4198 | 2024-04-22 03:50:27 |         MASTER-SAAO | (16h 53m 26.59s , -65d 11m 30.9s) |   C |    60 | 19.1 |        
    4198 | 2024-04-22 03:50:27 |         MASTER-SAAO | (16h 57m 48.08s , -65d 24m 47.4s) |   C |    60 | 18.9 |        
    4277 | 2024-04-22 03:51:46 |         MASTER-SAAO | (17h 33m 33.47s , -67d 07m 02.3s) |   C |    60 | 19.4 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB240415A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36225
SUBJECT: GRB 240415A: Swift-XRT refined Analysis
DATE:    24/04/22 07:22:59 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.ac.uk>

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

We have analysed 5.4 ks of XRT data for GRB 240415A, from 3.3 ks to
26.8 ks after the  BAT trigger. The data comprise 281 s in Windowed
Timing (WT) mode with the remainder in Photon Counting (PC) mode. 

The light curve can be modelled with a power-law decay with a decay
index of alpha=0.97 (+/-0.09).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.18 (+/-0.16). The
best-fitting absorption column is  2.2 (+/-0.5) x 10^21 cm^-2, in
excess of the Galactic value of 2.5 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 (4.9 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      2.2 (+/-0.5) x 10^21 cm^-2
Galactic foreground: 2.5 x 10^20 cm^-2
Excess significance: 6.4 sigma
Photon index:      2.18 (+/-0.16)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01221874.

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


GRB_name: GRB240415B
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36226
SUBJECT: GRB 240415B: Swift-XRT observations
DATE:    24/04/22 07:23:17 GMT
FROM:    Phil Evans at U of Leicester <pae9@star.le.ac.uk>

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

Swift-XRT has performed follow-up observations of the
Swift/BAT-detected burst GRB 240415B, collecting 3.4 ks of Photon
Counting (PC) mode data between T0+86.1 ks and T0+115.2 ks. 

Four uncatalogued X-ray sources have been detected consistent with
being within 493 arcsec of the Swift/BAT position, 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.
Details of these sources are given below:

Source 2:
  RA (J2000):  132.2001  =  08:48:48.03
  Dec (J2000): -27.0714  =  -27:04:17.2
  Error: 6.4 arcsec (radius, 90% conf.)
  Count-rate: (9.5 [+10.4, -8.3])e-4 ct s^-1   
  Distance: 374 arcsec from Swift/BAT position.

Source 3:
  RA (J2000):  132.3176  =  08:49:16.23
  Dec (J2000): -27.1553  =  -27:09:19.0
  Error: 6.6 arcsec (radius, 90% conf.)
  Count-rate: (2.6 [+1.6, -1.3])e-3 ct s^-1   
  Distance: 306 arcsec from Swift/BAT position.
  Flux: (1.32 [+0.83, -0.68])e-12 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 6:
  RA (J2000):  132.3018  =  08:49:12.44
  Dec (J2000): -27.1242  =  -27:07:27.0
  Error: 5.5 arcsec (radius, 90% conf.)
  Count-rate: (3.4 [+1.6, -1.3])e-3 ct s^-1   
  Distance: 200 arcsec from Swift/BAT position.
  Flux: (4.6 [+2.2, -1.8])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 7:
  RA (J2000):  132.4111  =  08:49:38.66
  Dec (J2000): -27.0674  =  -27:04:02.8
  Error: 5.6 arcsec (radius, 90% conf.)
  Count-rate: (3.6 [+1.8, -1.5])e-3 ct s^-1   
  Distance: 301 arcsec from Swift/BAT position.
  Flux: (8.8 [+4.5, -3.6])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Three uncatalogued sources were also detected too far from the GRB
position to be likely afterglow candidates.

The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
https://www.swift.ac.uk/ToO_GRBs/00021684.

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


GRB_name: GRB240414A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36228
SUBJECT: GRB 240414A: LBT optical detection
DATE:    24/04/22 14:43:25 GMT
FROM:    Andrea Rossi at INAF <andrea.rossi@inaf.it>

A. Rossi, E. Maiorano, E. Palazzi  (INAF-OAS), M . De Pasquale (Univ. of Messina), report on behalf of the CIBO collaboration:

We observed the field of GRB 240414A (Caputo et al. GCN 36083) simultaneously in the blue and red arms with the g'-, r'-, and z'-bands with the MODS instrument mounted on LBT (Mt Graham, AZ, USA). Observations were obtained at the midtime 05:41 UT on 2024-04-14, 3 hours and 20 minutes after the burst trigger.

We detect the optical transient (Schneider et al., GCN  36084, Aryan et al., GCN  36094, Dutton et al., GCN  36097, Xu et al., GCN  36105, Pankov et al., GCN  36113, Wang et al., GCN 36131) in all bands and we measure a preliminary AB magnitudes r'=19.1+-0.1, calibrated against SDSS field stars, and not corrected for the foreground Galactic extinction.

We acknowledge the excellent support from the LBTO and LBT-INAF staff, particularly A. Cardwell, J. Williams, F. Cusano and D. Paris, in obtaining these observations.


GRB_name: GRB240414A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36229
SUBJECT: GRB 240414A: AMI-LA radio observations
DATE:    24/04/22 15:06:17 GMT
FROM:    Lauren Rhodes at Oxford <lauren.rhodes@physics.ox.ac.uk>

Lauren Rhodes, Rob Fender (Oxford), Dave Green, Dave Titterington (Cambridge) report:

We observed the field of the afterglow candidate GRB 240414A (GCN #36083) with the Arcminute Microkelvin Imager Large-Array (AMI-LA) at 15.5 GHz beginning at 18:54UT on 20-Apr-2024 for a total of 4 hours. The flux standard 3c286 was used to calibrate the bandpass response and flux scale of the AMI-LA and J1219+4829 was used as an interleaved complex gain calibrator.

We do not detect any radio emission at the position of the afterglow candidate as reported in GCN #36102 at a 3 sigma upper limit of 297uJy/beam.

We thank the staff at the Mullard Radio Astronomy Observatory for carrying out these observations and operating the AMI-LA.


GRB_name: GRB240414A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36231
SUBJECT: GRB 240414A: radio detection with the VLA
DATE:    24/04/22 16:59:02 GMT
FROM:    Stefano Giarratana at University of Bologna <s.giarratana@ira.inaf.it>

S. Giarratana (INAF-OAB), M. Giroletti (INAF-IRA),
G. Ghirlanda (INAF-OAB), N. Di Lalla (Stanford Univ.),
N. Omodei (Stanford Univ.)

At 01:42:45 UT on 2024 April 17 (T_mid = 2.99 days post-burst) the
Karl G. Jansky VLA started observing the field of GRB 240414A
(Caputo et al., GCN 36083) at a central frequency of 6 and 10 GHz.

The standard J1331+3030 (3C286) was used as bandpass and flux density
calibrator, while J1217+5835 was used as complex gain calibrator.

From a preliminary analysis, an unresolved radio source is clearly
detected at both frequencies at a position:

RA: 12:19:08.08 +- 0.01
Dec: +56:44:28.7 +- 0.2

The surface brightness peak is 40 uJy/beam and 60 uJy/beam at 6
and 10 GHz, respectively. The r.m.s. noise level of the images is
7 uJy/beam at both 6 and 10 GHz.

The synthesized beams are 4.1 x 3.0 arcsec (PA: 70deg) at 6 GHz
and 2.7 x 1.9 arcsec (PA: 76deg) at 10 GHz.

While no source is detected at the aforementioned position in previous
radio surveys (FIRST, NVSS, VLASS), their r.m.s. noise levels (1sigma)
is above 100 uJy/b, well above the derived surface brightness peak.
Therefore, we cannot exclude the contribution from the GRB host galaxy yet.

We would like to thank the staff of the VLA for approving, executing,
and processing the observations.

The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc.

These observations were carried out as part of project SF161095,
approved in the framework of the Fermi - NRAO joint program agreement.


GRB_name: GRB240421A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36232
SUBJECT: GRB 240421A: Glowbug gamma-ray detection
DATE:    24/04/22 18:09:31 GMT
FROM:    C.C. Cheung at Naval Research Lab <Teddy.Cheung@nrl.navy.mil>

C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report:
 
The Glowbug gamma-ray telescope [1,2], operating on the International Space Station, reports the detection of GRB 240421A, which was also detected by Fermi/GBM (GCN 36204).
 
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2024-04-21 05:21:56.632 with a duration of 2.0 s and a total significance of about 11.3 sigma.  The light curve comprises a double-peaked structure.
 
The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS.
 
Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC.  It was launched on 2023 March 15 aboard the Department of Defense Space Test Programâ€™s STP-H9 to the ISS.  The detector comprises 12 large-area (15 cm x 15 cm) CsI:Tl panels covering the surface of a half cube, and two hexagonal (5-cm diameter, 10-cm length) CLLB scintillators, giving it a large field of view (instantaneous FoV ~2/3 sky) over a wide energy band of 50 keV to >2 MeV.
 
[1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959
[2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O
[3] Goldstein, A. et al. 2020, ApJ 895, 40, arXiv :1909.03006
 
Distribution Statement A: Approved for public release.  Distribution is unlimited.


GRB_name: GRB240419A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36250
SUBJECT: GRB 240419A: Possible ATCA radio detection
DATE:    24/04/23 09:51:22 GMT
FROM:    Gemma Anderson at Curtin U <gemma.anderson@curtin.edu.au>

S. Chastain (UNM), G. E. Anderson (Curtin University), J. K. Leung (U. Toronto/HUJI), L. Rhodes (U. Oxford), S. D. Ryder (Macquarie), A. Gulati (U. Sydney), A. J. van der Horst (GWU), on behalf of the PanRadio GRB collaboration

The Australia Telescope Compact Array (ATCA) performed rapid follow-up observations of GRB 240419A (Siegel et al., GCN 36169) at 5.5, 9, and 18 GHz as part of the Long-term ATCA "PanRadio GRB" follow-up programme C3542 (PI. Anderson). ATCA began observing at 2024-04-19 04:00 UT (2.2 hours post-burst) up until 12:30 UT. In our preliminary analysis, we have a marginal detect of 63 +/- 18 microJy/beam at 18 GHz that is coincident with the enhanced XRT position (Goad et al., GCN 36174). We obtain 3 sigma upper limits of 39 and 42 microJy/beam at 5.5 and 9.0, respectively. Further observations are planned.

We thank the CSIRO Space and Astronomy staff for supporting these observations. We acknowledge the Gomeroi people as the traditional owners of the Observatory site. The Australia Telescope Compact Array is part of the Australia Telescope National Facility
(https://ror.org/05qajvd42) which is funded by the Australian Government for operation as a National Facility managed by CSIRO.


GRB_name: GRB240402B
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36253
SUBJECT: LXT240402A/GRB240402B: Chandra X-ray detection
DATE:    24/04/23 12:55:40 GMT
FROM:    muskan.yadav@students.uniroma2.eu

M. Yadav, E. Troja, Y. -H. Yang, and R. L. Becerra (U. Rome) report:

Following the detection of the fast X-ray transient LXT 240402A (Xu et al., GCN 36016) associated with GRB 240402B (Wang et al., GCN 36017), we performed observations of the field with the Chandra X-ray Observatory starting at UT 00:48 on April 15, 2024 for a total exposure of 16 ks.
An X-ray source is detected with high significance at the location of the optical counterpart (Yang at al., GCN 36094).
Using the spectral parameters of the EP-FXT detection (Jia et al., GCN 36022) we derive an X-ray flux of 8*10^-14 erg s^-1 cm^-2 (0.5-10 keV), consistent with the Swift/XRT observations (Martin-Carrillo et al., GCN 36114).
We thank Pat Slane and the CXO staff for quickly arranging and executing the observations.


GRB_name: GRB240418A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36254
SUBJECT: GRB 240418A: Swift-BAT refined analysis
DATE:    24/04/23 12:59:27 GMT
FROM:    Mike Moss at NASA GSFC <mikejmoss3@gmail.com>

D. M. Palmer (LANL), S. D. Barthelmy (GSFC),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),
M. J. Moss (GSFC), T. Parsotan (GSFC),
T. Sakamoto (AGU), M. H. Siegel (PSU)
(i.e. the Swift-BAT team):
 
Using the data set from T-60 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 240418A (trigger #1222885)
(Siegel, et al., GCN Circ. 36162).  The BAT ground-calculated position is
RA, Dec = 239.342, 23.632 deg which is
   RA(J2000)  =  15h 57m 22.0s
   Dec(J2000) = +23d 37' 54.4"
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 79%.
 
The mask-weighted light curve shows a single, dim pulse peaking at T0+5 s.
The T90 (15-350 keV) is 12.00 +- 3.61 sec (estimated error including systematics).
 
The time-averaged spectrum from T-0.47 to T+12.53 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.99 +- 0.31.  The fluence in the 15-150 keV band is 2.3 +- 0.5 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T+4.53 sec in the 15-150 keV band
is 0.5 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.
 
The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1222885


GRB_name: GRB240419A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36255
SUBJECT: GRB 240419A: Swift-BAT refined analysis
DATE:    24/04/23 13:00:27 GMT
FROM:    Mike Moss at NASA GSFC <mikejmoss3@gmail.com>

T. Parsotan (GSFC), S. D. Barthelmy (GSFC),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),
M. J. Moss (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. H. Siegel (PSU)
(i.e. the Swift-BAT team):
 
Using the data set from T-60 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 240419A (trigger #1222955)
(Siegel, et al., GCN Circ. 36169).  The BAT ground-calculated position is
RA, Dec = 94.505, -44.964 deg which is
   RA(J2000)  =  06h 18m 01.3s
   Dec(J2000) = -44d 57' 50.2"
with an uncertainty of 3.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 89%.
 
The mask-weighted light curve shows two dim pulses at T0-7 s and T0+0 s,
respectively.
The T90 (15-350 keV) is 3.00 +- 1.41 sec (estimated error including systematics).
 
The time-averaged spectrum from T-0.43 to T+2.57 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.71 +- 0.38.  The fluence in the 15-150 keV band is 8.4 +- 2.1 x 10^-08 erg/cm2.
The 1-sec peak photon flux measured from T+0.57 sec in the 15-150 keV band
is 0.6 +- 0.1 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.
 
The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1222955


GRB_name: GRB240421B
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36269
SUBJECT: GRB 240421B: GRBAlpha detection
DATE:    24/04/24 03:33:17 GMT
FROM:    Marianna DafÄÃ­kovÃ¡ at Masaryk University <500025@mail.muni.cz>

M. Dafcikova, J. Ripa, M. Kolar (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner (Masaryk U.), M. Ohno, H. Takahashi (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), N. Husarikova, F. Munz , M. Topinka, M. Duriskova, L. Szakszonova, J.-P. Breuer, 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.), Y. Uchida, H. Poon, H. Matake (Hiroshima U.), N. Uchida (ISAS/JAXA), 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.), N. Kogiso, M. Yoneyama (Osaka Metropolitan U.), M. Moritaki (U. Tokyo), T. Kano (U. Michigan) -- the GRBAlpha collaboration.

The long-duration GRB 240421B (Swift/BAT detection: GCN 36208; Fermi/GBM detection: GCN 36218; AstroSat detection: GCN 36223; Konus/Wind detection trigger at 2024-04-21 09:42:53.511 UT; INTEGRAL/SPI-ACS peak detection at 2024-04-21 ~09:42:54 UT) was observed by the GRBAlpha 1U CubeSat (Pal et al. 2023, A&A, 677, 40; https://ui.adsabs.harvard.edu/abs/2023A%26A...677A..40P/abstract).

The detection was confirmed at the peak time 2024-04-21 09:42:53.5 UTC. The T90 duration measured by GRBAlpha is 5.0 s and the overall significance during T90 reaches 11 sigma.

The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB240421B_GCN.pdf

All GRBAlpha detections are listed at: https://monoceros.physics.muni.cz/hea/GRBAlpha/
GRBAlpha, launched on 2021 March 22, is a demonstration mission for a future CubeSat 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. 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: GRB240419B
Detection_method: Fermi LAT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36283
SUBJECT: IceCube-240424A - IceCube observation of a high-energy neutrino candidate track-like event
DATE:    24/04/24 14:00:19 GMT
FROM:    A. Zegarelli at Ruhr University Bochum <azegarelli@icecube.wisc.edu>

The IceCube Collaboration (http://icecube.wisc.edu/) reports:

On 2024-04-24 at 01:49:26.0 UT IceCube detected a track-like event with a high probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_GOLD alert stream.  The average astrophysical neutrino purity for Gold alerts is 50%. This alert has an estimated false alarm rate of 1.225 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection.

After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/139315_50057906.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to:

Date: 2024-04-24
Time: 01:49:26.0 UT
RA: 327.08 (+2.06, -1.70 deg  90% PSF containment) J2000
Dec: 3.06 (+1.37, -1.33 deg 90% PSF containment) J2000

We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino.

Two Fermi-LAT sources (listed in the 4FGL-DR4 or 3FHL catalogs) are located in the 90% uncertainty region. The nearest gamma-ray source in either catalog is 4FGL J2149.6+0323 (J2149.8+0322 in the 3FHL catalog) at RA: 327.42 deg and DEC: 3.40 deg (0.5 deg away from the best-fit position). The second one is 4FGL J2146.8+0425 at RA: 326.71 deg and DEC: 4.43 deg, 1.4 deg away from the best-fit position. The former source is associated with a BL Lac object, while the latter is a blazar candidate of uncertain type.

Additionally, we note that a recent GRB triggered by the Swift Burst Alert Catalog (BAT) on April 19, 2024 (GRB 240419B, detection time 2024-04-19 12:22:52 UT, GCN Circular #36180), is contained within the 90% uncertainty region of the neutrino candidate event, ~1.7 deg from its best-fit position. 

The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc@icecube.wisc.edu


GRB_name: GRB240422A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36290
SUBJECT: GRB 240422A: Glowbug gamma-ray detection
DATE:    24/04/24 21:13:46 GMT
FROM:    C.C. Cheung at Naval Research Lab <Teddy.Cheung@nrl.navy.mil>

R. Woolf, C.C. Cheung, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report:
 
The Glowbug gamma-ray telescope [1,2], operating on the International Space Station, reports the detection of GRB 240422A, which was also detected by Fermi/GBM (GCN 36222).

The detection occurred during a time of high background, thus complicating the analysis.  Using an adaptive window with a resolution of 32-ms, the initial peak seen in the GBM light curve was recovered, with a burst onset determined to be 2024-04-22 02:40:55.400 with a duration of 4.1 s and a total significance of about 8.0 sigma.

The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS.
 
Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC.  It was launched on 2023 March 15 aboard the Department of Defense Space Test Programâ€™s STP-H9 to the ISS.  The detector comprises 12 large-area (15 cm x 15 cm) CsI:Tl panels covering the surface of a half cube, and two hexagonal (5-cm diameter, 10-cm length) CLLB scintillators, giving it a large field of view (instantaneous FoV ~2/3 sky) over a wide energy band of 50 keV to >2 MeV.
 
[1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959
[2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O
[3] Goldstein, A. et al. 2020, ApJ 895, 40, arXiv :1909.03006
 
Distribution Statement A: Approved for public release.  Distribution is unlimited.


GRB_name: GRB240421B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36291
SUBJECT: GRB 240421B: Swift-BAT refined analysis
DATE:    24/04/24 21:46:59 GMT
FROM:    Sibasish Laha at GSFC <sibasish.laha@nasa.gov>

S. D. Barthelmy (GSFC), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC),A. Y. Lien (U Tampa),
C. B. Markwardt (GSFC),M. J. Moss (GSFC),
D. M. Palmer (LANL), T. Parsotan (GSFC),
T. Sakamoto (AGU) (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 240421B (trigger #1223470)
(Williams, et al., GCN Circ. 36208).  The BAT ground-calculated position is
RA, Dec = 299.685, -14.878 deg which is
   RA(J2000)  =  19h 58m 48.03s
   Dec(J2000) =  -14d 51' 36.4"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 4%.

The BAT light curve shows a complex structure with a duration of ~ 40 sec.
T90 (15-350 keV) is 24.00 +- 9.22 sec (estimated error including systematics).

The time-averaged spectrum from T-30.4 to T+7.6 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 0.63 +- 0.52,
and Epeak of 81.3 +- 22.3 keV (chi squared 50.17 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 6.4 +- 0.5 x 10^-06 erg/cm2
and the 1-sec peak flux measured from T-0.36 sec in the 15-150 keV band is
14.1 +- 1.6 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.55 +- 0.10 (chi squared 61.45 for 57 d.o.f.).  All the quoted errors
are at the 90% confidence level.

The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1223470


GRB_name: GRB240419B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36292
SUBJECT: GRB 240419B: Swift-BAT refined analysis
DATE:    24/04/24 21:47:33 GMT
FROM:    Sibasish Laha at GSFC <sibasish.laha@nasa.gov>

T. Sakamoto (AGU), S. D. Barthelmy (GSFC),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),
M. J. Moss (GSFC), D. M. Palmer (LANL),
T. Parsotan (GSFC),(i.e. the Swift-BAT team):

Using the data set from T-61 to T+242 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 240419B (trigger #1223072)
(Dichiara, et al., GCN Circ. 36180).  The BAT ground-calculated position is
RA, Dec = 325.853, 4.299 deg which is
   RA(J2000)  =  21h 43m 24.7s
   Dec(J2000) = +04d 17' 58.2"
with an uncertainty of 3.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 43%.

The BAT light curve shows a complex structure with a duration of ~ 150 sec.
T90 (15-350 keV) is 132.16 +- 26.29 sec (estimated error including systematics).

The time-averaged spectrum from T-3.3 to T+159.5 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.92 +- 0.09.  The fluence in the 15-150 keV band is 4.1 +- 0.2 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+116.36 sec in the 15-150 keV band
is 2.4 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1223072


GRB_name: GRB240425A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36295
SUBJECT: GRB 240425A: Fermi GBM Final Real-time Localization
DATE:    24/04/25 00:33:16 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 00:21:20 UT on 25 Apr 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240425A (trigger 735697285.341006 / 240425015).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 227.7, Dec = 46.7 (J2000 degrees, equivalent to J2000 15h 10m, 46d 42'), with a statistical uncertainty of 3.6 degrees.

The angle from the Fermi LAT boresight is 86.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240425015/quicklook/glg_skymap_all_bn240425015.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240425015/quicklook/glg_healpix_all_bn240425015.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240425015/quicklook/glg_lc_medres34_bn240425015.gif


GRB_name: GRB240414A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36318
SUBJECT: GRB 240414A: NOEMA detection
DATE:    24/04/26 15:39:53 GMT
FROM:    Antonio de Ugarte Postigo at OCA <deugarte@oca.eu>

A. de Ugarte Postigo (CNRS/OCA & LAM), M. Bremer (IRAM), C. C. Thoene (ASU-CAS), J. F. Agui Fernandez (CAHA), S. Antier (OCA), S. Basa (LAM), M. Michalowski (AOI-AMU), D. A. Perley (LJMU), J.-G. Ducoin (CPPM) report:

We observed the field of GRB 240414A (Caputo et al. GCN 36083; Myers et al. GCN 36120; Cheung et al. GCN 36147) with the NOEMA interferometer, located at the Plateau de Bure (France). The observation, performed on the 23rd April, was tuned with sidebands at 74 and 90 GHz.

When combining all the data, we obtain a weak, 3-sigma detection at the position of the afterglow (Schneider et al. GCN 36084; Adami et al. GCN 36085; de Ugarte Postigo GCN 36087; Dutton et al. 36097; Turpin et al. GCN 36101; Osborne et al. GCN 36102; Dichiara et al. GCN 36104; Pankov et al. GCN 36113; Siegel et al. GCN 36115; de Ugarte Postigo et al. GCN 36117; Wang et al. GCN 36131; Rossi et al. GCN 36228; Rhodes et al. GCN 36229; Giarratana et al. GCN 36231) with a flux density of ~55 uJy.

Based on observations carried out under project number W23DI with the IRAM NOEMA Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).


GRB_name: GRB240426A
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36324
SUBJECT: GRB 240426A: AstroSat CZTI detection
DATE:    24/04/26 17:17:25 GMT
FROM:    Gaurav Waratkar at IIT Bombay <gauravwaratkar@iitb.ac.in>

G. Waratkar (IITB),  J. Joshi (IUCAA), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/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., 2021, JApA, 42, 73) showed the detection of a long-duration GRB 240426A. Inspection of INTEGRAL/SPI-ACS data also showed the detection of the burst.

The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed a single peak of emission that peaked at 2024-04-26 13:24:10.5 UTC. The measured peak count rate associated with the burst is 122 (+47, -1) counts/s above the background in the combined data of all quadrants, with a total of 1360 (+272, -248) counts. We caution that there is a 0.3 s readout dead time in CZT data during the burst which affects the calculated total counts. The local mean background count rate was 318 (+3, -3) counts/s. Using cumulative rates, we measure a T90 of 20 (+4, -3) s.

It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed a single peak of emission that peaked at 2024-04-26 13:24:09.6 UTC. The measured peak count rate is 403 (+69, -52) counts/s above the background in the combined Veto data of all quadrants, with a total of 3640 (+415, -459) counts. The local mean background count rate was 1412 (+6, -6) counts/s. We measure a T90 of 23 (+1, -3) s from the cumulative Veto light curve.

CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project.

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


GRB_name: GRB240428A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36339
SUBJECT: Fermi GRB 240428A: Global MASTER-Net observations report
DATE:    24/04/28 17:45:56 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>

V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik,  D. Vlasenko,
G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij
(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. Gress, N.M. Budnev, O.Ershova
(Irkutsk State University, API),

L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez
(INAOE, Guillermo Haro Astrophysics Observatory),

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

V. Yurkov, A. Gabovich
(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 240428A ( Fermi GBM team, GCN 36338) errorbox  8392 sec after notice time and 8401 sec after trigger time at 2024-04-28 17:22:55 UT, with upper limit up to  18.5 mag. The observations began at zenith distance = 65 deg. The sun  altitude  is -17.4 deg. 

The galactic latitude b = 75 deg., longitude l = 238 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2438479

We obtain a following upper limits.  

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

    8431 | 2024-04-28 17:22:55 |         MASTER-SAAO | (11h 49m 40.27s , +20d 18m 15.1s) |   C |    60 | 18.5 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB240429A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36345
SUBJECT: GRB 240429A: Fermi GBM Final Real-time Localization
DATE:    24/04/29 15:15:08 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 15:04:28 UT on 29 Apr 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240429A (trigger 736095873.926064 / 240429628).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 13.7, Dec = 18.5 (J2000 degrees, equivalent to J2000 00h 54m, 18d 30'), with a statistical uncertainty of 8.9 degrees.

The angle from the Fermi LAT boresight is 83.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240429628/quicklook/glg_skymap_all_bn240429628.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240429628/quicklook/glg_healpix_all_bn240429628.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240429628/quicklook/glg_lc_medres34_bn240429628.gif


GRB_name: GRB240425A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36350
SUBJECT: GRB 240425A: GRBAlpha detection
DATE:    24/04/29 20:23:19 GMT
FROM:    Marianna DafÄÃ­kovÃ¡ at Masaryk University <500025@mail.muni.cz>

M. Dafcikova, J. Ripa, M. Kolar (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner (Masaryk U.), M. Ohno, H. Takahashi (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), N. Husarikova, F. Munz , M. Topinka, M. Duriskova, L. Szakszonova, J.-P. Breuer, 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.), Y. Uchida, H. Poon, H. Matake (Hiroshima U.), N. Uchida (ISAS/JAXA), 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.), N. Kogiso, M. Yoneyama (Osaka Metropolitan U.), M. Moritaki (U. Tokyo), T. Kano (U. Michigan) -- the GRBAlpha collaboration.

The long-duration GRB 240425A (Fermi/GBM detection: GCN 36295; INTEGRAL/SPI-ACS peak detection at 2024-04-25 ~00:21:36 UT) was observed by the GRBAlpha 1U CubeSat (Pal et al. 2023, A&A, 677, 40; https://ui.adsabs.harvard.edu/abs/2023A%26A...677A..40P/abstract).

The detection was confirmed at the peak time 2024-04-25 00:21:16.5 UTC. The T90 duration measured by GRBAlpha is 27.5 s and the overall significance during T90 reaches 7.9 sigma.

The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB240425A_GCN.pdf

All GRBAlpha detections are listed at: https://monoceros.physics.muni.cz/hea/GRBAlpha/
GRBAlpha, launched on 2021 March 22, is a demonstration mission for a future CubeSat 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. 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: GRB240407A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36357
SUBJECT: GRB 240407A: VZLUSAT-2 detection
DATE:    24/05/01 08:58:40 GMT
FROM:    Marianna DafÄÃ­kovÃ¡ at Masaryk University <500025@mail.muni.cz>

M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory),  N. Werner  (Masaryk U.), M. Ohno (Hiroshima U.),  L. Meszaros, B. Csak (Konkoly Observatory), H. Takahashi (Hiroshima U.), F. Munz , M. Topinka, F. Hroch, N. Husarikova, J.-P. Breuer (Masaryk U.), J. Hudec, J. Kapus, M. Frajt, M. Rezenov (Spacemanic s.r.o), R. Laszlo (Needronix), G. Galgoczi (Wigner Research Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), Y. Fukazawa, K. Hirose, H. Matake (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.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gromes (VZLU), I. Vertat (FEL ZCU)  -- the VZLUSAT-2/GRB payload collaboration.

The long-duration GRB 240407A (Fermi/GBM detection: GCN 36044; Konus/Wind detection trigger at 2024-04-07 00:59:52.851 UT; INTEGRAL/SPI-ACS peak detection at 2024-04-07 ~00:59:58 UT) was detected by the GRB detector on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/).

The data acquisition was performed by the GRB detector unit no. 1. The detection was confirmed at the peak time 2024-04-07 00:59:52 UTC. The T90 duration is 13 s and the significance during T90 reaches 24 sigma.

The light curve obtained by VZLUSAT-2 is available here:
https://vzlusat2.konkoly.hu/static/share/GRB240407A_GCN_VZLUSAT2.pdf

All VZLUSAT-2 detections are listed at: https://monoceros.physics.muni.cz/hea/VZLUSAT-2/
The GRB detectors on VZLUSAT-2 are a demonstration payload for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). Two GRB modules of VZLUSAT-2 are placed in a perpendicular manner and each consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13 from Cape Canaveral.


GRB_name: GRB240408B
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36358
SUBJECT: GRB 240408B: VZLUSAT-2 detection
DATE:    24/05/01 08:59:13 GMT
FROM:    Marianna DafÄÃ­kovÃ¡ at Masaryk University <500025@mail.muni.cz>

M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory),  N. Werner  (Masaryk U.), M. Ohno (Hiroshima U.),  L. Meszaros, B. Csak (Konkoly Observatory), H. Takahashi (Hiroshima U.), F. Munz , M. Topinka, F. Hroch, N. Husarikova, J.-P. Breuer (Masaryk U.), J. Hudec, J. Kapus, M. Frajt, M. Rezenov (Spacemanic s.r.o), R. Laszlo (Needronix), G. Galgoczi (Wigner Research Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), Y. Fukazawa, K. Hirose, H. Matake (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.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gromes (VZLU), I. Vertat (FEL ZCU)  -- the VZLUSAT-2/GRB payload collaboration.

The long-duration GRB 240408B (AstroSat/CZTI detection: GCN 36051; GRBAlpha detection: GCN 36062; Konus/Wind detection trigger at 2024-04-08 00:10:06.236 UT; INTEGRAL/SPI-ACS peak detection at 2024-04-08 ~00:10:03 UT) was detected by the GRB detector on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/).

The data acquisition was performed by the GRB detector unit no. 1. The detection was confirmed at the peak time 2024-04-08 00:10:03 UTC. The T90 duration is 42 s and the significance during T90 reaches 15 sigma.

The light curve obtained by VZLUSAT-2 is available here:
https://vzlusat2.konkoly.hu/static/share/GRB240408B_GCN_VZLUSAT2.pdf

All VZLUSAT-2 detections are listed at: https://monoceros.physics.muni.cz/hea/VZLUSAT-2/
The GRB detectors on VZLUSAT-2 are a demonstration payload for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). Two GRB modules of VZLUSAT-2 are placed in a perpendicular manner and each consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13 from Cape Canaveral.


GRB_name: GRB240501B
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36360
SUBJECT: GRB 240501B: AstroSat CZTI detection
DATE:    24/05/01 14:50:54 GMT
FROM:    Gaurav Waratkar at IIT Bombay <gauravwaratkar@iitb.ac.in>

G. Waratkar (IITB),  J. Joshi (IUCAA), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/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., 2021, JApA, 42, 73) showed the detection of a long-duration GRB 240501B. Inspection of INTEGRAL/SPI-ACS data also showed the detection of the burst.

The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2024-05-01 10:43:40.5 UTC. The measured peak count rate associated with the burst is 496 (+47, -49) counts/s above the background in the combined data of three quadrants (out of four), with a total of 3754 (+358, -332) counts. The local mean background count rate was 352 (+2, -4) counts/s. Using cumulative rates, we measure a T90 of 27 (+2, -1) 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 2024-05-01 10:43:40.3 UTC. The measured peak count rate is 889 (+87, -51) counts/s above the background in the combined Veto data of all quadrants, with a total of 6798 (+706, -707) counts. The local mean background count rate was 1539 (+5, -6) counts/s. We measure a T90 of 28 (+3, -2) s from the cumulative Veto light curve.

CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project.

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


GRB_name: GRB240430A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36361
SUBJECT: GRB240430A: Fermi GBM Final Localization
DATE:    24/05/01 14:58:25 GMT
FROM:    CuÃ¡n de Barra at UCD <cuan.debarra@ucdconnect.ie>

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

At 19:21:19.72 UT on 30 Apr 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240430A (trigger 736197684 / 240430806).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 201.0, Dec = 1.5 (J2000 degrees, equivalent to J2000 +13h 24m, +01d 32') with a statistical uncertainty of 2.6 degrees.

The angle from the Fermi LAT boresight is 62 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240430806/quicklook/glg_skymap_all_bn240430806.png

The HEALPix FITS file, including the estimated localization systematic, can
be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240430806/quicklook/glg_healpix_all_bn240430806.fit

The GBM light curve can be found here:
http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240430806/quicklook/glg_lc_medres34_bn240430806.gif


GRB_name: GRB240425A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36363
SUBJECT: GRB 240425A: VZLUSAT-2 detection
DATE:    24/05/01 15:46:34 GMT
FROM:    Marianna DafÄÃ­kovÃ¡ at Masaryk University <500025@mail.muni.cz>

M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory),  N. Werner  (Masaryk U.), M. Ohno (Hiroshima U.),  L. Meszaros, B. Csak (Konkoly Observatory), H. Takahashi (Hiroshima U.), F. Munz , M. Topinka, F. Hroch, N. Husarikova, J.-P. Breuer (Masaryk U.), J. Hudec, J. Kapus, M. Frajt, M. Rezenov (Spacemanic s.r.o), R. Laszlo (Needronix), G. Galgoczi (Wigner Research Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), Y. Fukazawa, K. Hirose, H. Matake (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.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gromes (VZLU), I. Vertat (FEL ZCU)  -- the VZLUSAT-2/GRB payload collaboration.

The long-duration GRB 240425A (Fermi/GBM detection: GCN 36295; GRBAlpha detection: GCN 36350; INTEGRAL/SPI-ACS peak detection at 2024-04-25 ~00:21:36 UT) was detected by the GRB detector on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/).

The data acquisition was performed by the GRB detector unit no. 1. The detection was confirmed at the peak time 2024-04-25 00:21:35 UTC. The T90 duration is 30 s and the significance during T90 reaches 10 sigma.

The light curve obtained by VZLUSAT-2 is available here:
https://vzlusat2.konkoly.hu/static/share/GRB240425A_GCN_VZLUSAT2.pdf

All VZLUSAT-2 detections are listed at: https://monoceros.physics.muni.cz/hea/VZLUSAT-2/
The GRB detectors on VZLUSAT-2 are a demonstration payload for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). Two GRB modules of VZLUSAT-2 are placed in a perpendicular manner and each consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13 from Cape Canaveral.


GRB_name: GRB240426A
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36364
SUBJECT: GRB 240426A: VZLUSAT-2 detection
DATE:    24/05/01 15:46:56 GMT
FROM:    Marianna DafÄÃ­kovÃ¡ at Masaryk University <500025@mail.muni.cz>

M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory),  N. Werner  (Masaryk U.), M. Ohno (Hiroshima U.),  L. Meszaros, B. Csak (Konkoly Observatory), H. Takahashi (Hiroshima U.), F. Munz , M. Topinka, F. Hroch, N. Husarikova, J.-P. Breuer (Masaryk U.), J. Hudec, J. Kapus, M. Frajt, M. Rezenov (Spacemanic s.r.o), R. Laszlo (Needronix), G. Galgoczi (Wigner Research Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), Y. Fukazawa, K. Hirose, H. Matake (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.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gromes (VZLU), I. Vertat (FEL ZCU)  -- the VZLUSAT-2/GRB payload collaboration.

The long-duration GRB 240426A (AstroSat/CZTI detection: GCN 36324; Konus/Wind detection trigger at 2024-04-26 13:24:05.908 UT; INTEGRAL/SPI-ACS peak detection at 2024-04-26 ~13:24:08 UT) was detected by the GRB detector on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/).

The data acquisition was performed by the GRB detector unit no. 1. The detection was confirmed at the peak time 2024-04-26 13:24:05 UTC. The T90 duration is 27 s and the significance during T90 reaches 7.8 sigma.

The light curve obtained by VZLUSAT-2 is available here:
https://vzlusat2.konkoly.hu/static/share/GRB240426A_GCN_VZLUSAT2.pdf

All VZLUSAT-2 detections are listed at: https://monoceros.physics.muni.cz/hea/VZLUSAT-2/
The GRB detectors on VZLUSAT-2 are a demonstration payload for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). Two GRB modules of VZLUSAT-2 are placed in a perpendicular manner and each consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13 from Cape Canaveral.


GRB_name: GRB240501A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36366
SUBJECT: Fermi GRB 240501A: Global MASTER-Net observations report
DATE:    24/05/01 22:16:11 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>

V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik,  D. Vlasenko,
G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij
(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. Gress, N.M. Budnev, O.Ershova
(Irkutsk State University, API),

L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez
(INAOE, Guillermo Haro Astrophysics Observatory),

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

V. Yurkov, A. Gabovich
(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 240501A ( Fermi GBM team, GCN 36359) errorbox  36531 sec after notice time and 36564 sec after trigger time at 2024-05-01 21:03:58 UT, with upper limit up to  18.7 mag. The observations began at zenith distance = 78 deg. The sun  altitude  is -63.3 deg. 

The galactic latitude b = 33 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=2440919

We obtain a following upper limits.  

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

   36594 | 2024-05-01 21:03:58 |         MASTER-SAAO | (16h 53m 16.15s , +23d 49m 52.4s) |   C |    60 | 17.3 |        
   36834 | 2024-05-01 21:07:57 |         MASTER-SAAO | (16h 52m 07.87s , +25d 43m 11.6s) |   C |    60 | 17.2 |        
   36834 | 2024-05-01 21:07:57 |         MASTER-SAAO | (16h 50m 08.14s , +25d 56m 26.4s) |   C |    60 | 18.0 |        
   37606 | 2024-05-01 21:20:49 |         MASTER-SAAO | (16h 53m 13.91s , +23d 49m 17.4s) |   C |    60 | 17.6 |        
   37845 | 2024-05-01 21:24:48 |         MASTER-SAAO | (16h 52m 09.05s , +25d 42m 19.5s) |   C |    60 | 17.8 |        
   37845 | 2024-05-01 21:24:48 |         MASTER-SAAO | (16h 50m 08.97s , +25d 55m 36.1s) |   C |    60 | 18.1 |        
   38164 | 2024-05-01 21:30:08 |         MASTER-SAAO | (17h 09m 07.83s , +25d 43m 11.5s) |   C |    60 | 17.4 |        
   38164 | 2024-05-01 21:30:08 |         MASTER-SAAO | (17h 07m 08.17s , +25d 56m 31.5s) |   C |    60 | 18.0 |        
   38244 | 2024-05-01 21:31:27 |         MASTER-SAAO | (17h 09m 18.90s , +27d 36m 36.6s) |   C |    60 | 17.5 |        
   38244 | 2024-05-01 21:31:27 |         MASTER-SAAO | (17h 07m 17.37s , +27d 49m 56.7s) |   C |    60 | 18.1 |        
   38323 | 2024-05-01 21:32:47 |         MASTER-SAAO | (17h 09m 52.76s , +23d 49m 42.9s) |   C |    60 | 17.5 |        
   38323 | 2024-05-01 21:32:47 |         MASTER-SAAO | (17h 07m 54.74s , +24d 03m 02.5s) |   C |    60 | 17.9 |        
   38403 | 2024-05-01 21:34:07 |         MASTER-SAAO | (16h 52m 16.43s , +27d 37m 22.5s) |   C |    60 | 17.8 |        
   38403 | 2024-05-01 21:34:07 |         MASTER-SAAO | (16h 50m 14.54s , +27d 50m 42.8s) |   C |    60 | 18.1 |        
   38563 | 2024-05-01 21:36:47 |         MASTER-SAAO | (16h 53m 19.60s , +23d 48m 31.2s) |   C |    60 | 18.1 |        
   38723 | 2024-05-01 21:39:26 |         MASTER-SAAO | (17h 10m 49.86s , +29d 29m 43.5s) |   C |    60 | 17.4 |        
   38723 | 2024-05-01 21:39:26 |         MASTER-SAAO | (17h 08m 46.06s , +29d 43m 04.1s) |   C |    60 | 18.1 |        
   38802 | 2024-05-01 21:40:46 |         MASTER-SAAO | (16h 52m 15.63s , +25d 44m 21.8s) |   C |    60 | 18.3 |        
   38802 | 2024-05-01 21:40:46 |         MASTER-SAAO | (16h 50m 15.34s , +25d 57m 41.4s) |   C |    60 | 18.4 |        
   39122 | 2024-05-01 21:46:05 |         MASTER-SAAO | (17h 09m 02.87s , +25d 41m 47.7s) |   C |    60 | 17.9 |        
   39122 | 2024-05-01 21:46:05 |         MASTER-SAAO | (17h 07m 02.99s , +25d 55m 09.0s) |   C |    60 | 18.2 |        
   39201 | 2024-05-01 21:47:25 |         MASTER-SAAO | (17h 09m 26.70s , +27d 35m 54.8s) |   C |    60 | 17.6 |        
   39201 | 2024-05-01 21:47:25 |         MASTER-SAAO | (17h 07m 24.96s , +27d 49m 15.1s) |   C |    60 | 17.9 |        
   39281 | 2024-05-01 21:48:45 |         MASTER-SAAO | (17h 09m 55.70s , +23d 49m 26.1s) |   C |    60 | 18.3 |        
   39281 | 2024-05-01 21:48:45 |         MASTER-SAAO | (17h 07m 57.38s , +24d 02m 45.1s) |   C |    60 | 18.4 |        
   39361 | 2024-05-01 21:50:04 |         MASTER-SAAO | (16h 52m 13.52s , +27d 36m 33.4s) |   C |    60 | 18.4 |        
   39361 | 2024-05-01 21:50:04 |         MASTER-SAAO | (16h 50m 11.40s , +27d 49m 53.5s) |   C |    60 | 18.5 |        
   39520 | 2024-05-01 21:52:44 |         MASTER-SAAO | (17h 25m 55.79s , +25d 42m 09.2s) |   C |    60 | 17.7 |        
   39520 | 2024-05-01 21:52:44 |         MASTER-SAAO | (17h 23m 55.98s , +25d 55m 28.9s) |   C |    60 | 18.2 |        
   39600 | 2024-05-01 21:54:04 |         MASTER-SAAO | (17h 09m 52.24s , +22d 09m 04.1s) |   C |    60 | 18.6 |        
   39680 | 2024-05-01 21:55:24 |         MASTER-SAAO | (17h 10m 53.56s , +29d 30m 44.6s) |   C |    60 | 18.1 |        
   39680 | 2024-05-01 21:55:24 |         MASTER-SAAO | (17h 08m 49.58s , +29d 44m 05.5s) |   C |    60 | 18.5 |        
   39760 | 2024-05-01 21:56:43 |         MASTER-SAAO | (17h 26m 30.57s , +27d 35m 06.7s) |   C |    60 | 17.9 |        
   39760 | 2024-05-01 21:56:43 |         MASTER-SAAO | (17h 24m 28.92s , +27d 48m 27.4s) |   C |    60 | 18.4 |        
   39839 | 2024-05-01 21:58:03 |         MASTER-SAAO | (17h 24m 38.91s , +24d 00m 31.5s) |   C |    60 | 18.7 |        
   40083 | 2024-05-01 22:02:07 |         MASTER-SAAO | (17h 09m 09.51s , +25d 43m 30.0s) |   C |    60 | 18.6 |        
   40083 | 2024-05-01 22:02:07 |         MASTER-SAAO | (17h 07m 09.27s , +25d 56m 50.5s) |   C |    60 | 18.6 |        
   40163 | 2024-05-01 22:03:27 |         MASTER-SAAO | (17h 09m 22.16s , +27d 36m 53.9s) |   C |    60 | 18.4 |        
   40163 | 2024-05-01 22:03:27 |         MASTER-SAAO | (17h 07m 20.08s , +27d 50m 14.9s) |   C |    60 | 18.5 |        
   40243 | 2024-05-01 22:04:46 |         MASTER-SAAO | (17h 09m 53.61s , +23d 49m 53.2s) |   C |    60 | 18.7 |        
   40243 | 2024-05-01 22:04:46 |         MASTER-SAAO | (17h 07m 55.05s , +24d 03m 13.1s) |   C |    60 | 18.6 |        
   40322 | 2024-05-01 22:06:06 |         MASTER-SAAO | (16h 52m 17.94s , +27d 37m 36.6s) |   C |    60 | 18.6 |        
   40322 | 2024-05-01 22:06:06 |         MASTER-SAAO | (16h 50m 15.56s , +27d 50m 58.5s) |   C |    60 | 18.6 |        
   40402 | 2024-05-01 22:07:25 |         MASTER-SAAO | (16h 53m 20.45s , +29d 30m 35.1s) |   C |    60 | 18.6 |        
   40482 | 2024-05-01 22:08:45 |         MASTER-SAAO | (17h 24m 02.65s , +25d 54m 40.1s) |   C |    60 | 18.5 |        
   40482 | 2024-05-01 22:08:45 |         MASTER-SAAO | (17h 26m 02.39s , +25d 41m 18.2s) |   C |    60 | 18.3 |        
   40561 | 2024-05-01 22:10:05 |         MASTER-SAAO | (17h 09m 54.66s , +22d 08m 51.9s) |   C |    60 | 18.5 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB240502A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36368
SUBJECT: GRB 240502A: Fermi GBM Final Real-time Localization
DATE:    24/05/02 05:39:12 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 05:28:41 UT on 2 May 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240502A (trigger 736320526.884406 / 240502228).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 124.6, Dec = 20.7 (J2000 degrees, equivalent to J2000 08h 18m, 20d 41'), with a statistical uncertainty of 7.2 degrees.

The angle from the Fermi LAT boresight is 99.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240502228/quicklook/glg_skymap_all_bn240502228.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240502228/quicklook/glg_healpix_all_bn240502228.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240502228/quicklook/glg_lc_medres34_bn240502228.gif


GRB_name: GRB240502A
Detection_method: INTEGRAL
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  36369
SUBJECT: GRB 240502A long GRB detected by INTEGRAL
DATE:    24/05/02 06:17:59 GMT
FROM:    Sandro Mereghetti at IASF-Milano/INAF <sandro.mereghetti@inaf.it>


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

a gamma ray burst lasting about 25 s has been detected by IBAS in the  IBIS/ISGRI data at 05:28:37  UT of 2 May 2024.

The refined coordinates (J2000) are:
R.A.=  113.629 deg
DEC.=  +16.7244 deg
with an uncertainty of  2   arcmin (90% c.l.).

The burst had a fluence   of about 4e-7 erg/cmq in the 20-200 keV range

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


