TITLE: GCN CIRCULAR NUMBER: 42971 SUBJECT: GRB 251201B: Insight-HXMT/HE detection DATE: 25/12/03 14:29:33 GMT FROM: Yue Wang <m18509381757@163.com> Yue Wang, Chen-Wei Wang, Chao Zheng, and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team: At 2025-12-01T16:26:24.000 (T0), Insight-HXMT/HE detected a long-duration GRB 251201B, which is also detected by Fermi/GBM (Fermi GBM team, GCN #42923) and GECAM-B (Yue Wang et. al., GCN #42952). The Insight-HXMT/HE light curve mainly consists of a long pulse with a T90 of 42 +11/-8 s. The 1s peak rate, measured from T0+6.5 s, is 494 cnts/sec. Insight-HXMT/HE detected a total of 8654 counts from this burst. The Insight-HXMT /HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb251201B.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org View this GCN Circular online at https://gcn.nasa.gov/circulars/42971. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...