GRB 261113B

Xing-Hao Luo, Chen-Wei Wang, Chao Zheng, and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team:

At 2026-11-13T19:45:55.000 (T0), Insight-HXMT/HE detected the GRB 261113B, which is also detected by Fermi/GBM (Fermi GBM team, GCN#46281
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 ).
	
The Insight-HXMT/HE light curve mainly consists of multiple pulses with a T90 of 8.0 +3.5/-6.0 s. The 1s peak rate, measured from T0+0.25 s, is 811 cnts/sec. Insight-HXMT/HE detected a total of 1434 counts from this burst.

The HXMT/HE light curve can be found here:
https://www.bursthub.cn/gcn/2026/hxmtgrb261113B.png

All measurements above are made with the CsI detectors of Insight-HXMT/HE 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://hxmten.ihep.ac.cn/

The Fermi GBM team reports the detection of a likely LONG GRB.

"At 19:45:55.10 UT on 13 November 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 261113B (trigger 816291960/261113824).This trigger was initially classified as Distant Particles by the flight software, but is in fact a GRB.

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 168.2, Dec = 42.4 (J2000 degrees, equivalent to J2000 11h 12m 43.2s, +42d 21'), with a statistical uncertainty of 2.76 degrees.

The angle from the Fermi LAT boresight is 147 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn261113824/quicklook/glg_skymap_all_bn261113824.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/bn261113824/quicklook/glg_healpix_all_bn261113824.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn261113824/quicklook/glg_lc_medres34_bn261113824.gif"