TITLE:   GCN CIRCULAR
NUMBER:  41797
SUBJECT: GRB 250909B: Insight-HXMT detection
DATE:    25/09/11 15:16:08 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 2025-09-09T17:49:10.200 (T0), Insight-HXMT/HE detected the burst GRB 250909B, which is also detected by AstroSat (M. Tembhurnikar et al., GCN#41775), SVOM/GRM (Wang et al., GCN#41796) and Konus-Wind.

The Insight-HXMT/HE light curve mainly consists of multi-pulses with a T90 of 12.9 +1.2/-1.7 s. The 1s peak rate, measured from T0+0.250 s, is 5422 cnts/sec. The total counts from this burst is 23044 counts.

The HXMT/HE light curve can be found here:
https://www.bursthub.cn//admin/static/hxmtgrb250909B.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.