GRB 250502B
GCN Circular 40314
Subject
GRB 250502B: Fermi GBM Final Real-time Localization
Date
2025-05-02T10:24:22Z (a month ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
The Fermi GBM team reports the detection of a likely LONG GRB
At 10:13:53 UT on 2 May 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250502B (trigger 767873638.16821 / 250502426).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 312.3, Dec = 14.5 (J2000 degrees, equivalent to J2000 20h 49m, 14d 30'), with a statistical uncertainty of 2.3 degrees.
The angle from the Fermi LAT boresight is 56.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250502426/quicklook/glg_skymap_all_bn250502426.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250502426/quicklook/glg_healpix_all_bn250502426.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250502426/quicklook/glg_lc_medres34_bn250502426.gif
GCN Circular 40317
Subject
Fermi GRB 250502B: Global MASTER-Net observations report
Date
2025-05-02T11:31:09Z (a month ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko,
G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A.Sosnovskij (CrAO),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 250502B ( Fermi GBM team, GCN 40314) errorbox 74 sec after notice time and 110 sec after trigger time at 2025-05-02 10:15:44 UT, with upper limit up to 18.4 mag. Observations started at twilight. The observations began at zenith distance = 44 deg. The sun altitude is -11.2 deg.
The galactic latitude b = -18 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=2858681
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
121 | 2025-05-02 10:15:44 | MASTER-OAFA | (20h 40m 38.20s , +13d 02m 12.4s) | C | 20 | 17.2 |
121 | 2025-05-02 10:15:44 | MASTER-OAFA | (20h 49m 58.93s , +13d 25m 00.9s) | C | 20 | 18.3 |
155 | 2025-05-02 10:16:23 | MASTER-OAFA | (20h 40m 37.90s , +13d 02m 09.6s) | C | 10 | 16.9 |
166 | 2025-05-02 10:16:23 | MASTER-OAFA | (20h 49m 58.55s , +13d 24m 57.5s) | C | 30 | 18.4 |
205 | 2025-05-02 10:17:07 | MASTER-OAFA | (20h 43m 52.56s , +13d 09m 28.3s) | C | 20 | 17.2 |
215 | 2025-05-02 10:17:08 | MASTER-OAFA | (20h 53m 13.53s , +13d 32m 15.9s) | C | 40 | 18.4 |
256 | 2025-05-02 10:17:54 | MASTER-OAFA | (20h 43m 52.15s , +13d 09m 25.1s) | C | 30 | 17.2 |
266 | 2025-05-02 10:17:54 | MASTER-OAFA | (20h 53m 13.16s , +13d 32m 11.9s) | C | 50 | 18.3 |
317 | 2025-05-02 10:18:50 | MASTER-OAFA | (20h 43m 51.68s , +13d 09m 20.3s) | C | 40 | 17.2 |
328 | 2025-05-02 10:18:50 | MASTER-OAFA | (20h 53m 12.71s , +13d 32m 06.8s) | C | 60 | 18.2 |
388 | 2025-05-02 10:19:56 | MASTER-OAFA | (20h 43m 51.16s , +13d 09m 15.6s) | C | 50 | 17.1 |
399 | 2025-05-02 10:19:56 | MASTER-OAFA | (20h 53m 12.22s , +13d 32m 01.2s) | C | 70 | 18.0 |
474 | 2025-05-02 10:21:12 | MASTER-OAFA | (20h 43m 50.52s , +13d 09m 08.5s) | C | 70 | 17.0 |
581 | 2025-05-02 10:22:48 | MASTER-OAFA | (20h 43m 49.65s , +13d 08m 59.4s) | C | 90 | 16.8 |
715 | 2025-05-02 10:24:52 | MASTER-OAFA | (20h 39m 05.67s , +13d 52m 50.6s) | C | 110 | 16.6 |
828 | 2025-05-02 10:27:21 | MASTER-OAFA | (20h 36m 00.38s , +11d 56m 35.1s) | C | 40 | 16.4 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 40324
Subject
GRB 250502B: DDOTI Optical Observations
Date
2025-05-02T15:03:40Z (a month ago)
From
sahil.atri@students.uniroma2.eu
Via
Web form
Sahil Atri (U Roma), Rosa L. Becerra (U Roma), Alan M. Watson (UNAM), Camila Angulo Valdez (UNAM), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Océlotl López (UNAM), Margarita Pereyra (UNAM) and Eleonora Troja (U Roma) report:
We observed the field of the GRB 250502B detected by Fermi/GBM (Fermi GBM Team, GCN 40314) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir (http://ddoti.astroscu.unam.mx) on the night of 2025-05-02 UTC.
DDOTI observed the Fermi/GBM error region (Fermi GBM Team, GCN Circ. 40314), covering about 80% of the error region. DDOTI observed from 10:35 UTC to 11:41 UTC (from T+0.4 h to T+1.5 h after the trigger) and obtained a total exposure of 26.4 minutes, alternating with other scientific programs.
Comparing our observations to the USNO-B1 and Pan-STARRS PS1 DR2 catalogues, we detect no any uncatalogued source at the position reported by Fermi GBM Team, GCN Circ. 40314) down to a 10-sigma limiting AB magnitude of:
w > 19.71.
Nevertheless, by serendipity, the field observed included the position at RA= 20:58:11.46, DEC=+14:55:28.9, coincident with SN 2025ian/ATLAS25ebg (SN Ia) (https://www.wis-tns.org/object/2025ian/discovery-cert; Tonry et al., TNS Astronomical Transient Report No. 252299). We measured with w=17.91+/0.08 at T+10.1 days.
These values are not corrected for the Galactic extinction.
We thank the staff of the Observatorio Astronómico Nacional on the Sierra of San Pedro Mártir.
GCN Circular 40332
Subject
GRB 250502B: AstroSat CZTI detection
Date
2025-05-03T09:01:01Z (a month ago)
From
Gaurav Waratkar at IIT Bombay <gauravwaratkar@iitb.ac.in>
Via
Web form
M. Tembhurnikar (IUCAA), G. Waratkar (IITB), 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 250502B which was also detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 40314).
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 2025-05-02 10:13:59 UTC. The measured peak count rate associated with the burst is 73 (+34, -4) counts/s above the background in the combined data of two quadrants (out of four), with a total of 379 (+260, -70) counts. The local mean background count rate was 141 (+1, -4) counts/s. Using cumulative rates, we measure a T90 of 17 (+4, -12) s.
The source 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 2025-05-02 10:13:52 UTC. The measured peak count rate associated with the burst is 158 (+75, -9) counts/s above the background in the combined data of all quadrants, with a total of 1160 (+408, -455) counts. The local mean background count rate was 1232 (+6, -6) counts/s. We measure a T90 of 18 (+3, -9) 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