GCN 44785: GRB 260601B/EP260601a: Insight-HXMT detection

2026-06-03T06:12:43.040Z | rev 0 | event: GRB 260601B
Chen-Wei Wang, Zheng-Hang Yu, Shao-Lin Xiong, Cheng-Kui Li, and Chao Zheng report on behalf of the Insight-HXMT team:

At 2026-06-01T19:12:49.900 (T0), Insight-HXMT/HE detected the possible long duration Type I burst GRB 260601B/EP260601a, which is also detected by GECAM-B (Yu et al., GCN #44767; Wang et al., GCN #44768), NuSTAR (Waratkar et al., GCN #44771), CGBM (S. Sugita et al., GCN #44773) and EP (Yang et al., GCN #44766).
	
The Insight-HXMT/HE light curve mainly consists of a possible precursor and then a short pulse followed by a long emission with a T90 of 76.0 +4.5/-4.0 s. 
The total counts from this burst is 175433 counts.

The HXMT/HE light curve can be found here:
https://www.bursthub.cn//admin/static/hxmtgrb260601B.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.