GCN Circular 45820
GRB 261005A: Glowbug gamma-ray detection
From: C.C. Cheung at Naval Research Lab
Issued: 2026-10-06 16:10 UTC
Type: GRB, Gamma-ray Transient
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 261005A, which was also detected by Fermi/GBM (GCN 45811).
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-10-05 20:19:00.664 with a duration of 5.1 s and a total significance of about 13.5 sigma. The light curve comprises a single peak.
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.
[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.
Every one of the gamma-ray bursts GCN reports is posted here.
Relayed automatically from NASA's General Coordinates Network.
Transient Alerts » in reply to GRB 261005A
In plain words Routine
A burst of gamma rays, the most energetic form of light, reached Earth on 5 October 2026 and was recorded by three separate space telescopes: Fermi, Glowbug (an experiment on the International Space Station) and China's GECAM-B. Fermi places it in the constellation region around 22h 39m right ascension and +5.5 degrees declination, but only roughly, with an uncertainty of about 6 degrees. Fermi classed it as a likely long burst, the kind usually linked to the collapse of a massive star. Glowbug measured a single peak lasting about 5 seconds, and GECAM-B estimated about 9 seconds with a large margin of error. No distance, afterglow or visible-light counterpart has been reported so far.
How unusual is it? This is a typical single-pulse long gamma-ray burst, of a kind Fermi and Swift see a few hundred times a year, with only a rough location and no distance or afterglow reported. A measured distance or a detected afterglow would make it notable.
Written by an AI model (claude-sonnet-5-5) from the official reports in this thread, and rewritten as new reports arrived (version 2); last updated . It may contain mistakes: the reports themselves are the authority.
GRB 261005A: Glowbug gamma-ray detection