GRB 260805C
GCN Circular 45346
Subject
GRB 260805C: CALET Gamma-Ray Burst Monitor detection
Date
2026-08-10T13:48:32Z (15 days ago)
From
Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>
Via
Web form
N. Cannady (GSFC), 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), 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 260805C
at 07:27:40.04 UTC on 5 August 2026 (trigger #1469950046;
https://cgbm.calet.jp/cgbm_trigger/flight/1469950046/index.html).
No real-time CGBM GCN notice was distributed about this trigger because
the real-time communication from the ISS was off (loss of signal).
This event was also reported by Glowbug (Cheung et al., GCN #45292).
The burst signal was seen by all CGBM detectors.
The burst light curve shows a single pulse starting
at T-0.6 s and ending at T+8.0 s.
The T90 and T50 durations measured with the SGM data are 7.6 +/- 0.5 s
and 4.4 +/- 0.5 s in the 40-1000 keV band, respectively.
The ground-processed light curve is available at:
https://cgbm.calet.jp/cgbm_trigger/ground/1469950046/
The CALET data used in this analysis were provided by
the Waseda CALET Operation Center located at Waseda University.
GCN Circular 45292
Subject
GRB 260805C: Glowbug gamma-ray detection
Date
2026-08-05T21:24:48Z (19 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 260805C.
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-08-05 07:27:39.496 with a duration of ~12 s and a total significance of about 36 sigma. The light curve comprises a single FRED-shaped pulse. Additional lower-level emission up to ~T0+22s 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.