TITLE:   GCN CIRCULAR
NUMBER:  40489
SUBJECT: GRB 250516B: Insight-HXMT detection
DATE:    25/05/19 12:37:22 GMT
FROM:    Chenwei Wang at IHEP <cwwang@ihep.ac.cn>

Chen-Wei Wang, Shao-Lin Xiong, and Jin-Peng Zhang report on behalf of the Insight-HXMT team:

At 2025-05-16T06:31:34.7 (T0), Insight-HXMT/HE detected the bright long burst GRB 250516B, which is also detected by GECAM-B (Wang et al., GCN #40469), NuSTAR (B. Grefenstette et al., GCN #40484) and Konus-Wind.
	
The Insight-HXMT/HE light curve mainly consists of multiple pulses with a T90 of 39.6 +0.3/-0.2 s. 
The 1s peak rate, measured from T0+13.1 s, is 27175 cnts/sec. 
The total counts from this burst is 423316 counts.

The HXMT/HE light curve can be found here:
https://www.bursthub.cn//admin/static/hxmtgrb250516B.png

All measurements above are made with the CsI detectors operating in the regular mode with the energy range of about 30-1000 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.