GRB 260407A
GCN Circular 44246
Subject
GRB 260407A: GECAM-A detection
Date
2026-04-09T11:19:26Z (16 days ago)
From
guohx@ihep.ac.cn
Via
Web form
Hao-Xuan Guo, Shao-Lin Xiong, Peng Zhang, Yan-Qiu Zhang, Chen-Wei Wang (IHEP) report on behalf of the GECAM team:
GECAM-A detected a long burst, GRB 260407A, at 2026-04-07T09:11:07.950 UTC (denoted as T0), which was also observed by Fermi GBM (GCN #44226), Glowbug (C.C. Cheung et al., GCN #44237), CALET (M. L. Cherry et al., GCN #44242) and Insight-HXMT/HE (Hao-Xuan Guo et al., GCN #44245).
According to the GECAM-A light curves in about 40-6000 keV, this burst mainly consists of a single pulse with a duration (T90) of 19.5 +4.5/-6.5 s.
The GECAM-A light curve can be found here:
https://www.bursthub.cn//admin/static/gecamagrb260407A.png
Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two microsatellites (GECAM-A and GECAM-B) launched in Dec. 2020.
As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS).
GCN Circular 44245
Subject
GRB 260407A: Insight-HXMT/HE detection
Date
2026-04-09T11:05:54Z (16 days ago)
From
guohx@ihep.ac.cn
Via
Web form
Hao-Xuan Guo, Chen-Wei Wang, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng (IHEP) report on behalf of the Insight-HXMT team:
At 2026-04-07T09:11:07.000 (T0), Insight-HXMT/HE detected a long burst, GRB 260407A, which is also detected by Fermi GBM (GCN #44226), Glowbug (C.C. Cheung et al., GCN #44237) and CALET (M. L. Cherry et al., GCN #44242).
The Insight-HXMT/HE light curve mainly consists of a single pulse with a total duration (T90) of 23.5 +16/-9 s. The 1s peak rate, measured from T0+0.25 s, is 493 cnts/sec. Insight-HXMT/HE detected a total of 4651 counts from this burst.
The Insight-HXMT /HE light curve can be found here:
https://www.bursthub.cn//admin/static/hxmtgrb260407A.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 44242
Subject
GRB 260407A: CALET Gamma-Ray Burst Monitor detection
Date
2026-04-09T03:43:44Z (16 days ago)
From
Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>
Via
Web form
M. L. Cherry (LSU), 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), S. Ricciarini (U of Florence),
P. S. Marrocchesi (U of Siena),
and the CALET collaboration:
The long GRB 260407A (Fermi GBM Final Real-time Localization: Fermi GBM team,
GCN Circ. 44226; Glowbug gamma-ray detection: Cheung et al., GCN Circ 44237)
triggered the CALET Gamma-ray Burst Monitor (CGBM) at 09:11:06.11 UTC on 7 April 2026
(https://cgbm.calet.jp/cgbm_trigger/flight/1459588274/index.html).
The burst signal was seen by all CGBM detectors.
The burst light curve shows a single pulse that starts
at T-0.5 sec, peaks at T+1.6 sec, and ends at T+27.1 sec.
The T90 and T50 durations measured by the SGM data are 22.6 +/- 5.0 sec
and 7.0 +/- 1.0 sec (40-1000 keV), respectively.
The ground-processed light curve is available at
https://cgbm.calet.jp/cgbm_trigger/ground/1459588274
The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at Waseda University.
GCN Circular 44237
Subject
GRB 260407A: Glowbug gamma-ray detection
Date
2026-04-08T14:32:22Z (17 days ago)
From
C.C. Cheung at Naval Research Lab <Teddy.Cheung@nrl.navy.mil>
Via
Web form
C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report:
The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 260407A, which was detected by Fermi/GBM (GCN 44226).
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-04-07 09:11:06.112 with a duration of 4.1 s and a total significance of about 9.6 sigma. The light curve comprises a single peak. Additional lower-level emission up to ~T0+10s, as well as earlier emission beginning ~T0-2s, may be present in the Glowbug light curve at low significance.
The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS.
Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12.
[1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959
[2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O
[3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108
Distribution Statement A: Approved for public release. Distribution is unlimited.
GCN Circular 44226
Subject
GRB 260407A: Fermi GBM Final Real-time Localization
Date
2026-04-07T09:21:29Z (18 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 09:11:07 UT on 7 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260407A (trigger 797245872.223582 / 260407383).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 71.4, Dec = 28.2 (J2000 degrees, equivalent to J2000 04h 45m, 28d 11'), with a statistical uncertainty of 2.1 degrees.
The angle from the Fermi LAT boresight is 61.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260407383/quicklook/glg_skymap_all_bn260407383.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/bn260407383/quicklook/glg_healpix_all_bn260407383.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260407383/quicklook/glg_lc_medres34_bn260407383.gif