TITLE: GCN CIRCULAR NUMBER: 42056 SUBJECT: GRB 251001A: Insight-HXMT detection DATE: 25/10/02 14:27:57 GMT FROM: Chenwei Wang at IHEP cwwang@ihep.ac.cn

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

At 2025-10-01T02:40:57.600 (T0), Insight-HXMT/HE was trigger by the burst GRB 251001A, which is also detected by Fermi/GBM (Fermi GBM Team, GCN#42034).

The Insight-HXMT/HE light curve mainly consists of multi-pulses with a T90 of 8.2 +/-1.6 s. The 1s peak rate, measured from T0+5.300 s, is 759 cnts/sec. The total counts from this burst is 2439 counts.

The HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb251001A.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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