TITLE: GCN CIRCULAR NUMBER: 39163 SUBJECT: GRB 250204B: SVOM/GRM observation of a likely short burst DATE: 25/02/06 06:08:28 GMT FROM: yqzhang_cl@163.com

SVOM/GRM team: Yan-Qiu Zhang, Wen-Jun Tan, Chen-Wei Wang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)

SVOM/ECLAIRs team: Nicolas Dagoneau(CEA), Maria-GraziaBernardini (INAF-OAB), Jean-Luc Atteia (IRAP)

report on behalf of the SVOM team:

SVOM/GRM was triggered in-flight by a likely short burst GRB 250204B (sb25020402) at 2025-02-04T06:41:14.100 UTC (T0), which was also observed by Fermi/GBM (Fermi GBM team, GCN #39141) and AstroSat CZTI (A. Dasgupta et al., GCN #39142).

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 2.92 +/- 0.08 s in the 15-300 keV band.

In addition, the position of this burst, as determined by Fermi/GBM (GCN #39141, RA: 2.35 deg, DEC: 29.70 deg, Error: 2.80 deg), is located at about 137 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/svgrb250204B.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: Yan-Qiu Zhang (IHEP) (zhangyanqiu@ihep.ac.cn)

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