GCN Circular 46111
Subject
GRB 261024D: SVOM/GRM observation
Event
Date
2026-10-30T13:30:23Z (2 days ago)
From
Xinghao Luo at IHEP <2952704891@qq.com>
Via
Web form
SVOM/GRM team: Xing-Hao Luo, Yue Wang, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Oliver Godet (IRAP)
Report on behalf of the SVOM team:
SVOM/GRM was triggered in-flight by GRB 261024D (SVOM trigger reference: sb26102402) at 2026-10-24T21:33:06.000 (T0), which is also detected by AstroSat CZTI (A. Goyal et.al., GCN#46040), NuSTAR (G. Waratkar et.al., GCN#46051), Glowbug gamma-ray telescope (C. C. Cheung et.al., GCN#46053), GECAM-B (Xing-Hao Luo et.al., GCN#46061) and Insight-HXMT (Xing-Hao Luo et.al., GCN#46065).
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-value of 11.0 +2.5/-1.0 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn/gcn/2026/svgrb261024D.png
In addition, the position of this burst, as determined by GECAM-B (RA = 208.64 deg, Dec = 25.1 deg, with a statistical uncertainty of 5.46 degrees, Xing-Hao Luo et.al., GCN #46061), is located at about 155 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. However, ECLAIRs detected this burst by reflection onto the Earth atmosphere since the Earth fraction was 1 at the time of the burst.
With this localization, the time-averaged spectrum from T0-1.5 to T0+11 s is best fitted by a power law function with an exponential high energy cutoff. The power law index is -1.32 +0.17/-0.16 and the cutoff energy, parameterized as Epeak, is 131 +11/-10 keV. The event fluence (10-1000 keV) in this time interval is (2.22 +0.13/−0.12)E-05 erg/cm^2.
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: Xing-Hao Luo (IHEP) (luoxh@ihep.ac.cn)