TITLE: GCN CIRCULAR NUMBER: 39493 SUBJECT: GRB 250225B: SVOM/GRM observation of a long burst DATE: 25/02/26 14:06:50 GMT FROM: yqzhang_cl@163.com
SVOM/GRM team: Yan-Qiu Zhang, Chao Zheng, Chen-Wei Wang, Shi-Jie Zheng, Wen-Jun Tan, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Nicolas Dagoneau (CEA), Maria-Grazia Bernardini (INAF-OAB), Jean-Luc Atteia (IRAP)
report on behalf of the SVOM team:
SVOM/GRM was triggered on-ground by a long burst GRB 250225B at 2025-02-25T19:39:14.000 (T0), which was also observed by Swift/BAT (M.A. Williams et al., GCN #39473), Fermi/GBM (triNum #762205158) and INTEGRAL/SPI-ACS (triNum #11068).
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 293.0 +/- 31.2 s in the 15-5000 keV band.
In addition, the position of this burst, as determined by Swift/BAT (GCN #39473, RA: 306.145 deg, DEC: -41.4845 deg, Error: 3 arcmin), is located at about 113 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/svgrb250225B.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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