GCN Circular 45741
Subject
GRB 260924A: SVOM/GRM observation
Event
Date
2026-09-25T09:22:35Z (18 days ago)
From
yzh807926@163.com
Via
Web form
SVOM/GRM team: Zheng-Hang Yu, Wen-Jun Tan, Yue Wang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Olivier Godet (IRAP)
Report on behalf of the SVOM team:
SVOM/GRM was triggered in-flight by GRB 260924A (SVOM trigger reference: sb26092401) at 2026-09-24T01:13:28.000 (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #45712), Swift (V. D'Elia et al., GCN #45713), AstroSat CZTI (S. Salunke, GCN #45720) and Fermi/LAT (A. Holzmann Airasca et al., GCN #45721).
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of two main episodes multiple pulses followed by a single pulse with a T90 of 338.0 +/-1.0 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn/gcn/2026/9/svgrb260924A.png
In addition, the position of this burst, as determined by Swift/XRT (RA = 133.76, Dec = 12.04, Error = 2.1 arcsec, GCN #45715), is located at about 78 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. ECLAIRs detected the burst mostly through the shield above 50 keV.
With this localization, the time-averaged spectrum from T0-10 to T0+400 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.90 +/-0.03 and the cutoff energy, parameterized as Epeak, is 535 +37/-33 keV. The event fluence (10-1000 keV) in this time interval is (3.35 +0.06/-0.07)E-04 erg/cm^2.
The 1s peak spectrum, measured from T0+339 to T0+340 s, if fitted by a power law function with an exponential high-energy cutoff, the power law index is -0.88 +0.04/-0.05 and the cutoff energy, parameterized as Epeak, is 943 +113/-95 keV. The flux (10-1000 keV) in this time interval is (6.87 +/-0.16)E-06 erg/cm^2/s.
The localization of GRB 260924A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn/gcn/2026/9/svgrb260924A_amati.png
The localization of GRB 260924A in the 'Yonetoku' relation diagram is shown at:
https://www.bursthub.cn/gcn/2026/9/svgrb260924A_yonetoku.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: Zheng-Hang Yu (IHEP) (zhyu@ihep.ac.cn)