TITLE: GCN CIRCULAR NUMBER: 38982 SUBJECT: GRB 250117A: GECAM observation of a short burst DATE: 25/01/19 12:49:03 GMT FROM: Chenwei Wang at IHEP cwwang@ihep.ac.cn

Chen-Wei Wang, Yan-Qiu Zhang, Jin-Peng Zhang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team:

GECAM-B was triggered in-flight by a short burst, GRB 250117A, at 2025-01-17T20:21:57.950 UTC (denoted as T0), which was also detected by Fermi/GBM, Konus-Wind and INTEGRAL/SPI-ACS.

According to the GECAM-B light curves in about 20-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of about 0.70 +0.25/-0.65 s.

The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecamgrb250117A.png

Using the automatic on-ground localization pipeline, GECAM-B localized this burst to the following position (J2000): Ra: 271.8 deg Dec: -23.2 deg Err: 7.6 deg (1-sigma, statistical only)

We note that GRB 250117A is located near the galactic disc, and its localization seems to be consistent with the position of GRB 250116A (Ra= 266.64 deg，Dec=-19.36 deg, Err=0.13 deg, GCN # 38963) within the error, which may suggest that both bursts possibly come from ssan interesting galactic source. More analysis is ongoing.

Follow-up observations of GRB 250117A and GRB 250116A are encouraged.

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).

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