GCN Circular 44423
Subject
GRB 260428A: GECAM-B detection of a possible long duration Type I burst
Event
Date
2026-04-29T15:24:26Z (9 days ago)
From
Chenwei Wang at IHEP <cwwang@ihep.ac.cn>
Via
Web form
Chen-Wei Wang, Shao-Lin Xiong, Chao Zheng, Zheng-Hang Yu (IHEP) report on behalf of GECAM team:
GECAM-B was triggered in-flight by a hard burst GRB 260428A at 2026-04-28T14:20:35.850 UTC (denoted as T0). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multi-pulses with a duration (T90) of 5.6 +6.8/-2.6 s, which is also detected by Fermi/GBM (Fermi GBM team, GCN#44415), AstroSat (A. Goyal et al., GCN#44421) and SVOM/GRM.
The GECAM-B light curve can be found here:
https://www.bursthub.cn//admin/static/gecambgrb260428A.png
The time-averaged spectrum from T0-0.6 s to T0+4.0 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.05 +0.24/-0.21 and the cutoff energy, parameterized as Epeak, is 1320 +690/-420 keV. The event fluence (10-1000 keV) in this time interval is (6.02 +0.42/-0.47)E-06 erg/cm^2. Thus GRB 260428A is consistent with Type I GRBs in the 'Amati' relation diagram, as shown at:
https://www.bursthub.cn//admin/static/gecambgrb260428A_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).