GCN Circular 42552
Subject
GRB 251103A: SVOM/GRM observation
Event
Date
2025-11-03T15:34:46Z (2 months ago)
From
Chenwei Wang at IHEP <cwwang@ihep.ac.cn>
Via
Web form
SVOM/GRM team: Chen-Wei Wang. Xing-Hao Luo, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Ulysse Jacob (LUPM)
Report on behalf of the SVOM team:
SVOM/GRM was triggered in-flight by a burst GRB 251103A (SVOM trigger reference: sb25110302) at 2025-11-03T04:46:28.000 UTC (T0), which is also detected by SVOM/ECLAIRs (Hu et al., GCN#42534) and Fermi/GBM (Fermi GBM Team, GCN#42536).
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a single pulse with a T90 of 8.6 +0.8/-0.8 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb251103A.png
In addition, the position of this burst, as determined by SVOM/ECLAIRs (RA= 146.8375, DEC= 16.1296, GCN#42534), is located at about 13 degrees from the SVOM optical axis.
With this localization, the time-averaged spectrum from T0-2 to T0+7 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.21 +0.06/-0.05 and the cutoff energy, parameterized as Epeak, is 185 +23/-18 keV. The event fluence (10-1000 keV) in this time interval is (8.18 +0.41/-0.38)E-06 erg/cm^2.
The 1s peak spectrum, measured from T0+0.2 to T0+1.2 s, is also best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.89 +0.06/-0.06 and the cutoff energy, parameterized as Epeak, is 198 +15/-13 keV. The flux (10-1000 keV) in this time interval is (2.61 +0.11/-0.10)E-06 erg/cm^2/s.
Assuming the redshift z=0.76 (L. Izzo et al., GCN#42540), the localization of GRB 251103A in the 'Amati' relation diagram is shown at:
https://www.bursthub.cn//admin/static/svgrb251103A_amati.png
And the localization in the 'Yonetoku' relation diagram is shown at:
https://www.bursthub.cn//admin/static/svgrb251103A_yonetoku.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 point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang@ihep.ac.cn)