TITLE: GCN CIRCULAR NUMBER: 43158 SUBJECT: GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645 DATE: 25/12/20 17:41:34 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 in-flight by a short soft burst GRB 251219A, at 2025-12-19T02:36:31.550 UTC (denoted as T0), which is also detected by SVOM/GRM. According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of a single pulse with a duration (T90) of 0.22 +0.08/-0.16 s. The signal is mainly detected in energy lower than 200 keV. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251219A.png GECAM-B localized this burst to the following position (J2000): Ra: 274.4 deg Dec: -4.8 deg Err: 4.3 deg (1-sigma, statistical only) We note that the localization is consistent with the magnetar SGR 1830-0645. The short duration and soft spectrum also suggest this is a magnetar X-ray burst. 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). View this GCN Circular online at https://gcn.nasa.gov/circulars/43158. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...