TITLE: GCN CIRCULAR NUMBER: 43171 SUBJECT: GRB 251220B: SVOM/GRM observation of a short burst DATE: 25/12/21 13:31:39 GMT FROM: Chenwei Wang at IHEP <cwwang@ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Marius Brunet, Sebastien Guillot (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a short burst GRB 251220B (SVOM trigger reference: sb25122004) at 2025-12-20T23:38:04.700 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN#43160). 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 0.28 +0.15/-0.10 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb251220B.png In addition, the position of this burst, as determined by Fermi/GBM(RA= 251.4, DEC= 47.9, ERR=6.4), is located at about 135 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. 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) View this GCN Circular online at https://gcn.nasa.gov/circulars/43171. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...