TITLE:   GCN CIRCULAR
NUMBER:  42190
SUBJECT: GRB 251009A: GECAM-B detection of a short burst
DATE:    25/10/10 16:22:21 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 the short burst GRB 251009A at 2025-10-09T15:58:56.300 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN#42179), SVOM/GRM (Wang et al., GCN#42185) and Insight-HXMT (Wang et al., GCN#42189). 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 0.14 +0.08/-0.08 s.

The GECAM-B light curve can be found here:
https://www.bursthub.cn//admin/static/gecambgrb251009A.png

Using the automatic on-ground localization pipeline, GECAM-B localized this burst to the following position (J2000): 
Ra: 103.2 deg 
Dec: 34.2 deg
Err: 21.4 deg (1-sigma, statistical only)

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).