TITLE: GCN CIRCULAR NUMBER: 39993 SUBJECT: GRB 250330B: SVOM/GRM observation of a short burst DATE: 25/04/01 04:33:43 GMT FROM: Yue Wang m18509381757@163.com

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

SVOM/ECLAIRs team: O. Godet, Jean-Luc Atteia (IRAP), Frédéric Piron (LUPM), Stéphane Schanne (CEA)

Report on behalf of the SVOM team:

SVOM/GRM was triggered in-flight by GRB 250330B (SVOM trigger reference: sb25033007) at 2025-03-30T21:52:22.100 (T0). This burst was also detected by Fermi/GBM (Fermi GBM Team, GCN 39951).

With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of single main pulse with a T90 of 0.48 +0.32/-0.11 s in the 15-5000 keV band.

In addition, ECLAlRs was taking data and did not trigger, since the position of this burst, as determined by Fermi/GBM (GCN 39951, RA: 114.1 deg, DEC: 13.3 deg, Error: 3.1 deg), is located at about 96.2 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/svgrb250330B.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: Yue Wang (IHEP) (yuewang@ihep.ac.cn)

View this GCN Circular online at https://gcn.nasa.gov/circulars/39993. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...