GCN Circular 46182
Subject
GRB 261029C: SVOM/GRM detection of a short burst
Event
Date
2026-11-07T08:24:34Z (17 hours ago)
From
zhangjinpeng@ihep.ac.cn
Via
Web form
SVOM/GRM team: Jin-Peng Zhang, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Olivier Godet, Marius Brunet (IRAP)
Report on behalf of the SVOM team:
SVOM/GRM was triggered by GRB 261029C in-flight at 2026-10-29T23:38:37.000 (T0) (SVOM trigger reference: sb26102904), which is also detected by AstroSat CZTI (Harsha K. H. et al, GCN #46129), Konus-Wind (D. Svinkin et al., GCN #46171) and Psyche (D. Svinkin et al., GCN #46159).
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst mainly consists of one pulse with a T90 of 0.25 +0.15/-0.05 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn/gcn/2026/svgrb261029C.png
In addition, the position of this burst, according to IPN localization (RA = 336.252, Dec = -1.683, D. Svinkin et al., GCN #46159), is located at about 95.6 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. ECLAIRs saw it through the shield above 50 keV.
With this localization, the time-averaged spectrum from T0-0.2 to T0+0.2 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.73 +0.14/-0.12 and the cutoff energy, parameterized as Epeak, is (1.33 +0.35/-0.26)E3 keV. The event fluence (10-1000 keV) in this time interval is (2.78 +0.17/-0.18)E-6 erg/cm^2.
The localization of GRB 261029C in the 'Amati' relation diagram is shown at:
https://www.bursthub.cn/gcn/2026/svgrb261029C_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/GRM point of contact for this burst is: Jin-Peng Zhang (IHEP) (zhangjinpeng@ihep.ac.cn)