TITLE:   GCN CIRCULAR
NUMBER:  43002
SUBJECT: GRB 251203A: Insight-HXMT/HE detection
DATE:    25/12/05 15:48:13 GMT
FROM:    renyz16607@163.com

Yang-Zhao Ren, Chen-Wei Wang, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng (IHEP) report on behalf of the Insight-HXMT team:

At 2025-12-03T08:18:50.250 (T0), Insight-HXMT/HE detected a long burst, GRB 251203A, which is also detected by Fermi/GBM (Fermi GBM team, GCN#42968), SVOM/GRM (Ren et al., GCN#42995), and GECAM-B (Ren et al., GCN#42996). 

The Insight-HXMT/HE light curve mainly consists of multiple pulses with T90 of 11 +5/-5 s. The 1s peak rate, measured from T0-0.5 s, is 351 cnts/sec. Insight-HXMT/HE detected a total of 1399 counts from this burst.  

The Insight-HXMT /HE light curve can be found here: 
https://www.bursthub.cn//admin/static/hxmtgrb251203A.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://www.hxmt.org