TITLE: GCN CIRCULAR NUMBER: 40489 SUBJECT: GRB 250516B: Insight-HXMT detection DATE: 25/05/19 12:37:22 GMT FROM: Chenwei Wang at IHEP <cwwang@ihep.ac.cn> Chen-Wei Wang, Shao-Lin Xiong, and Jin-Peng Zhang report on behalf of the Insight-HXMT team: At 2025-05-16T06:31:34.7 (T0), Insight-HXMT/HE detected the bright long burst GRB 250516B, which is also detected by GECAM-B (Wang et al., GCN #40469), NuSTAR (B. Grefenstette et al., GCN #40484) and Konus-Wind. The Insight-HXMT/HE light curve mainly consists of multiple pulses with a T90 of 39.6 +0.3/-0.2 s. The 1s peak rate, measured from T0+13.1 s, is 27175 cnts/sec. The total counts from this burst is 423316 counts. The HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb250516B.png All measurements above are made with the CsI detectors operating in the regular mode with the energy range of about 30-1000 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/40489. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...