GRB 250305A
GCN Circular 39597
Subject
GRB 250305A: Fermi GBM Final Real-time Localization
Date
2025-03-05T15:39:31Z (3 months 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 15:28:57 UT on 5 Mar 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250305A (trigger 762881342.919284 / 250305645).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 223.7, Dec = -3.0 (J2000 degrees, equivalent to J2000 14h 54m, -3d 00'), with a statistical uncertainty of 5.0 degrees.
The angle from the Fermi LAT boresight is 60.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250305645/quicklook/glg_skymap_all_bn250305645.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/bn250305645/quicklook/glg_healpix_all_bn250305645.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250305645/quicklook/glg_lc_medres34_bn250305645.gif
GCN Circular 39599
Subject
Fermi GRB 250305A: Global MASTER-Net observations report
Date
2025-03-05T21:32:49Z (3 months ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko,
A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, 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. 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-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 250305A ( Fermi GBM team, GCN 39597) errorbox 20388 sec after notice time and 20424 sec after trigger time at 2025-03-05 21:09:22 UT, with upper limit up to 18.6 mag. The observations began at zenith distance = 78 deg. The sun altitude is -45.2 deg.
The galactic latitude b = 47 deg., longitude l = 353 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2801332
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
20455 | 2025-03-05 21:09:22 | MASTER-SAAO | (14h 34m 50.28s , -02d 29m 23.3s) | C | 60 | 18.3 |
20534 | 2025-03-05 21:10:41 | MASTER-SAAO | (14h 42m 45.22s , -02d 30m 38.4s) | C | 60 | 18.4 |
20613 | 2025-03-05 21:12:01 | MASTER-SAAO | (14h 36m 36.01s , -04d 22m 25.4s) | C | 60 | 18.6 |
20772 | 2025-03-05 21:14:39 | MASTER-SAAO | (14h 44m 39.80s , -04d 22m 36.6s) | C | 60 | 18.5 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 39602
Subject
GRB 250305A: SVOM/GRM observation of a burst
Date
2025-03-06T09:51:52Z (3 months ago)
From
zhangjinpeng@ihep.ac.cn
Via
Web form
SVOM/GRM team: Jin-Peng Zhang, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Nicolas Dagoneau (CEA), Maria-Grazia Bernardini (INAF-OAB), Jean-Luc Atteia (IRAP), Frédéric Piron (LUPM)
Report on behalf of the SVOM team:
SVOM/GRM was triggered in-flight by GRB 250305A (SVOM burst-id sb25030508) at 2025-03-05T15:28:58.100 (T0), which was also observed by Fermi/GBM (Fermi GBM team, GCN #39597).
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multi-pulses with a T90 of 4.6 +1.5/-0.9 s in the 15-5000 keV band.
In addition, the position of this burst, as determined by Fermi/GBM (GCN #39597, RA: 223.7 deg, DEC: -3.0 deg, Error: 5.0 deg), is located at about 63 degrees from the SVOM optical axis, and outside the ECLAIRs field of view.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb250305A.png
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS.
The SVOM/GRM point of contact for this burst is: Jin-Peng Zhang (IHEP) (zhangjinpeng@ihep.ac.cn)
GCN Circular 39613
Subject
GRB 250305A: AstroSat CZTI detection
Date
2025-03-07T12:11:29Z (3 months ago)
From
Gaurav Waratkar at IIT Bombay <gauravwaratkar@iitb.ac.in>
Via
Web form
M. Tembhurnikar (IUCAA), J. Joshi (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 GRB 250305A which was also detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 39597), and SVOM/GRM (Jin-Peng Zhang et al., GCN Circ. 39602).
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-03-05 15:28:58.3 UTC. The measured peak count rate associated with the burst is 517 (+151, -123) counts/s above the background in the combined data of all quadrants, with a total of 135 (+57, -41) 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 271 (+8, -14) counts/s. Using cumulative rates, we measure a T90 of 0.9 (+0.2, -0.7) s.
The source was also weakly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The measured peak count rate associated with the burst is 161 (+53, -55) counts/s above the background in the combined data of all quadrants, with a total of 298 (+140, –157) counts. The local mean background count rate was 897.1 (+5.5, –6.3) counts/s. Due to the intrinsic 1 s binning of veto data, we cannot reliably estimate a T90 from it.
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