GRB 260415A
GCN Circular 44372
Subject
GRB 260415A: CALET Gamma-Ray Burst Monitor detection
Date
2026-04-21T09:56:37Z (3 days ago)
From
Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>
Via
Web form
A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU),
K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii,
Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U),
N. Cannady (GSFC), M. L. Cherry (LSU), S. Ricciarini (U of Florence),
P. S. Marrocchesi (U of Siena),
and the CALET collaboration:
The CALET Gamma-ray Burst Monitor (CGBM) detected GRB 260415A
(Fermi GBM Final Real-time Localization: Fermi GBM team, GCN #44299;
Insight-HXMT/HE detection: Ren et al., GCN #44311) at 04:43:58.34 UTC on 15 April 2026
(https://cgbm.calet.jp/cgbm_trigger/flight/1460263432/index.html).
The burst signal was seen by all CGBM detectors.
The burst light curve shows a double-peaked structure starting
at T-1.5 s, peaking at T+30.1 s, and ending at T+41.1 s.
The T90 and T50 durations measured with the SGM data are 36.2 +/- 1.5 s
and 19.9 +/- 1.9 s (40-1000 keV), respectively.
The ground-processed light curve is available at
https://cgbm.calet.jp/cgbm_trigger/ground/1460263432/
The CALET data used in this analysis were provided by
the Waseda CALET Operation Center located at Waseda University.
GCN Circular 44311
Subject
GRB 260415A: Insight-HXMT/HE detection
Date
2026-04-16T12:39:40Z (8 days ago)
From
renyz16607@163.com
Via
Web form
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 2026-04-15T04:44:27.200 (T0), Insight-HXMT/HE detected a long burst, GRB 260415A, which is also detected by Fermi/GBM (Fermi GBM team, GCN #44299).
The Insight-HXMT/HE light curve mainly consists of multi-pulses with T90 of 39 +3/-2 s. The 1s peak rate, measured from T0+0.75 s, is 2212 cnts/sec. Insight-HXMT/HE detected a total of 27305 counts from this burst.
The Insight-HXMT /HE light curve can be found here:
https://www.bursthub.cn/admin/static/hxmtgrb260415A.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/
GCN Circular 44299
Subject
GRB 260415A: Fermi GBM Final Real-time Localization
Date
2026-04-15T04:54:40Z (9 days 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 04:43:59 UT on 15 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260415A (trigger 797921044.314306 / 260415197).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 58.5, Dec = -24.0 (J2000 degrees, equivalent to J2000 03h 53m, -24d 00'), with a statistical uncertainty of 5.5 degrees.
The angle from the Fermi LAT boresight is 92.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260415197/quicklook/glg_skymap_all_bn260415197.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/bn260415197/quicklook/glg_healpix_all_bn260415197.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260415197/quicklook/glg_lc_medres34_bn260415197.gif