TITLE: GCN CIRCULAR NUMBER: 41929 SUBJECT: GRB 250920C: SVOM/GRM observation DATE: 25/09/21 12:22:56 GMT FROM: Chenwei Wang at IHEP <cwwang@ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang. Wen-Jun Tan, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Jean-Luc Atteia (IRAP), Stéphane Schanne (CEA) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a burst GRB 250920C (SVOM trigger reference: sb25092008) at 2025-09-20T15:25:17.400 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN#41895) and Swift/BAT (R. Gupta, GCN#41904). 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 39.5 +0.5/-1.0 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250920C.png In addition, the position of this burst, as determined by Swift/BAT (RA= 51.459, DEC= -29.646, GCN#41904), is located at about 81 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view, but this burst is still detected by ECLAIRs through the shield. With this localization, the time-averaged spectrum from T0-2 to T0+41 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.08 +0.08/-0.08 and the cutoff energy, parameterized as Epeak, is 166 +19/-15 keV. The event fluence (10-1000 keV) in this time interval is (3.36 +0.17/-0.16)E-05 erg/cm^2. With the redshift of z=1.40 (R. Sanchez-Ramirez et al., GCN#41928), the localization of GRB 250920C in the 'Amati' relation diagram is consistent with type II GRBs, as shown at: https://www.bursthub.cn//admin/static/svgrb250920C_amati.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) View this GCN Circular online at https://gcn.nasa.gov/circulars/41929. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...