GRB 260409A
GCN Circular 44267
Subject
GRB 260409A: Insight-HXMT/HE detection
Date
2026-04-11T15:14:51Z (a month ago)
From
zhangjinpeng@ihep.ac.cn
Via
Web form
Jin-Peng Zhang, Chen-Wei Wang, Chao Zheng, and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team:
At 2026-04-09T17:32:46.000 (T0), Insight-HXMT/HE detected GRB 260409A, which is also detected by Fermi/GBM (Fermi GBM Team, GCN #44249).
The Insight-HXMT/HE light curve mainly consists of several pulses with a T90 of 43 +6/-3 s. The 1 s peak rate, measured from T0+8.5 s, is 919 cnts/sec. Insight-HXMT/HE detected a total of 11547 counts from this burst.
The Insight-HXMT/HE light curve can be found here:
https://www.bursthub.cn//admin/static/hxmtgrb260409A.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://hxmten.ihep.ac.cn
GCN Circular 44249
Subject
GRB 260409A: Fermi GBM Final Real-time Localization
Date
2026-04-09T17:43:22Z (a month ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
The Fermi GBM team reports the detection of a likely LONG GRB
At 17:32:45 UT on 9 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260409A (trigger 797448770.671026 / 260409731).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 298.8, Dec = 61.6 (J2000 degrees, equivalent to J2000 19h 55m, 61d 36'), with a statistical uncertainty of 2.0 degrees.
The angle from the Fermi LAT boresight is 121.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260409731/quicklook/glg_skymap_all_bn260409731.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260409731/quicklook/glg_healpix_all_bn260409731.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260409731/quicklook/glg_lc_medres34_bn260409731.gif