TITLE:   GCN CIRCULAR
NUMBER:  40841
SUBJECT: GRB 250625A: GECAM-B detection
DATE:    25/06/26 14:18:47 GMT
FROM:    Chenwei Wang at IHEP <cwwang@ihep.ac.cn>

Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team:

GECAM-B was triggered on-ground by GRB 250625A at 2025-06-25T16:04:56 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN#40824), Swift/BAT (David Palmer et al., GCN#40825), Fermi/LAT (Davide Depalo et al., GCN#40836). According to the GECAM-B light curves in about 40-6000 keV, this burst mainly consists of a single pulse with a duration (T90) of 6.0 +3.5/-5.5 s.

The GECAM-B light curve can be found here:
https://www.bursthub.cn//admin/static/gecamgrb250625A.png

The time-averaged spectrum from T0 to T0+4 s is best fitted by a power law function. The power law index is -1.52 +0.29/-0.20. The event fluence (10-1000 keV) in this time interval is (1.39 +/-0.24)E-06 erg/cm^2.

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).