TITLE: GCN CIRCULAR NUMBER: 43244 SUBJECT: GRB 251226A: GECAM-B detection DATE: 25/12/27 17:22:35 GMT FROM: Chenwei Wang at IHEP <cwwang@ihep.ac.cn> Chen-Wei Wang, Wen-Jun Tan, Xue-Yuan Zao, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by a long burst GRB 251226A, at 2025-12-26T08:01:02.550 UTC (denoted as T0), which is also detected by SVOM/GRM and HXMT. According to the GECAM-B light curve in about 70-6000 keV, this burst mainly consists of a precursor-like pulse followed by a multi-pulses main emission with a duration (T90) of 35.9 +3.4/-6.0 s. We note that the quiescent time between the precursor-like pulse and the main emission is relatively short. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251226A.png GECAM-B in-flight localization of this burst is (J2000): Ra: 260.2 deg Dec: 47.0 deg Err: 9.1 deg (1-sigma, statistical only) We note that the localization may be improved since this burst is not detected by Fermi/GBM. 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/43244. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...