TITLE: GCN CIRCULAR NUMBER: 41284 SUBJECT: GRB 250804B: Insight-HXMT detection DATE: 25/08/08 11:41:51 GMT FROM: Chenwei Wang at IHEP cwwang@ihep.ac.cn

Chen-Wei Wang, Shao-Lin Xiong, and Chao Zheng report on behalf of the Insight-HXMT team:

At 2025-08-04T04:44:51.600 (T0), Insight-HXMT/HE detected the short burst GRB 250804B, which is also detected by SVOM/GRM (Wang et al., GCN #41229).

The Insight-HXMT/HE light curve mainly consists of a weak precursor and a single main pulse with a T90 of 0.47 +0.14/-0.18 s. The total counts from this burst is 2193 counts.

The HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb250804B.png

All measurements above are made with the CsI detectors 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.

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