GCN Circular 46108
Subject
GRB 261029A: GECAM-B detection of a bright burst
Event
Date
2026-10-30T08:00:02Z (2 days ago)
From
yzh807926@163.com
Via
Web form
Zheng-Hang Yu, Shao-Lin Xiong (IHEP) report on behalf of GECAM team:
GECAM-B was triggered in-flight by a burst GRB 261029A at 2026-10-29T01:27:04.300 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #46071), SVOM/ECLAIRs (Hatsune Goto et al., GCN #46072), CALET (P. S. Marrocchesi., GCN #46095) and SVOM/GRM (Yu et al., GCN #46096). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 40.0 +/-0.6 s.
The GECAM-B light curve can be found here:
https://www.bursthub.cn/gcn/2026/10/gecambgrb261029A.png
The time-averaged spectrum from T0-5.0 to T0+50.0 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is 1.05 +0.04/-0.05 and the cutoff energy, parameterized as Epeak, is 914 +88/-81 keV. The event fluence (10-1000 keV) in this time interval is (1.09 +/-0.01) E-04 erg/cm^2.
With the measured redshift z=3.27 (L. Cotter et al., GCN 46081), we calculate the isotropic energy Eiso is about 3.6E54 erg. Thus GRB 261029A is well consistent with Type II GRBs in the 'Amati' relation diagram, as shown at:
https://www.bursthub.cn/gcn/2026/10/gecambgrb261029A_amati.png
Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS).