GCN Circular 38967

Yue Wang, Shao-Lin Xiong, Chen-Wei Wang, Chao Zheng, Shi-Jie Zheng, Cheng-Kui Li, Wen-Long Zhang, Yan-Qiu Zhang report on behalf of the GECAM team:

GECAM-B was triggered in-flight by a long burst, GRB 250116A, at 2025-01-16T12:33:59.550 UTC (T0), which was also observed by Fermi/GBM (GCN # 38962) and Fermi/LAT (GCN # 38963).

According to the GECAM-B light curves in about 20-1000 keV, this burst mainly consists of multiple pulses with a duration (T90) of about 15.5（+0.4,-0.6）s.

The GECAM-B light curve can be found here:
https://www.bursthub.cn//admin/static/gecamgrb250116A.png

GECAM location is consistent with the Fermi/LAT position within the error. 

We notice that the location is close to the Galactic plane and the light curve pattern is somewhat atypical for GRB but more similar to SGR, though the duration is much longer than SGR.

We note that these results are based on in-flight trigger data and thus very preliminary. Refined analysis will be reported later.

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission originally consists of two microsatellites (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).