TITLE: GCN CIRCULAR NUMBER: 42198 SUBJECT: GRB 251009B: SVOM/GRM observation of short GRB DATE: 25/10/11 08:12:07 GMT FROM: Chenwei Wang at IHEP cwwang@ihep.ac.cn

SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)

SVOM/ECLAIRs team: Stéphane Schanne (CEA), Jean-Luc Atteia (IRAP)

Report on behalf of the SVOM team:

SVOM/GRM was triggered on-ground by a short burst GRB 251009B at 2025-10-09T01:51:15.350 UTC (T0), which is also detected by Insight-HXMT (Wang et al., GCN#42187), Glowbug (C.C. Cheung et al., GCN#42188).

With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a double spikes with a T90 of 1.2 +0.75/-0.45 s in the 15-5000 keV band, the signal mainly appears above 100 keV. No significant signal is detected by ECLAIRs, suggesting the burst is outside the ECLAIRs FoV.

The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb251009B.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)

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