TITLE: GCN CIRCULAR NUMBER: 44267 SUBJECT: GRB 260409A: Insight-HXMT/HE detection DATE: 26/04/11 15:14:51 GMT FROM: zhangjinpeng@ihep.ac.cn Jin-Peng Zhang, Chen-Wei Wang, Chao Zheng, and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team: At 2026-04-09T17:32:46.000 (T0), Insight-HXMT/HE detected GRB 260409A, which is also detected by Fermi/GBM (Fermi GBM Team, GCN #44249). The Insight-HXMT/HE light curve mainly consists of several pulses with a T90 of 43 +6/-3 s. The 1 s peak rate, measured from T0+8.5 s, is 919 cnts/sec. Insight-HXMT/HE detected a total of 11547 counts from this burst. The Insight-HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb260409A.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the low gain mode with the energy range of about 300-3000 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://hxmten.ihep.ac.cn View this GCN Circular online at https://gcn.nasa.gov/circulars/44267. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...