GCN Circular 45810
GRB 261003A: Glowbug gamma-ray detection of a likely short burst
From: C.C. Cheung at Naval Research Lab
Issued: 2026-10-05 17:16 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 the likely short GRB 261003A, which was also detected by Fermi/GBM (GCN 45797).
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-10-03 01:18:35.072 with a duration of 0.1 s and a total significance of about 9.6 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
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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 261003A
In plain words Routine
On 3 October 2026, NASA's Fermi space telescope picked up a brief flash of gamma rays (the most energetic form of light) from a spot in the northern sky, in the direction of the constellation Cygnus. The flash looks like a short gamma-ray burst, a type that usually lasts under about two seconds and is often linked to the merger of two dense dead stars. Glowbug, a gamma-ray detector on the International Space Station, also saw it, as a single peak lasting about a tenth of a second. Fermi could only place it within a large patch of sky, roughly 20 degrees across, and a Russian-led robotic telescope network searched part of that area about 77 minutes later and found no new visible source down to a certain faintness. No distance or afterglow (fading light from the explosion) has been reported so far.
How unusual is it? Short bursts are a regular catch for Fermi, and this one has only a rough location, no afterglow and no measured distance. It would become more interesting if a faint afterglow or a host galaxy were found, or if a gravitational-wave signal were tied to it.
Written by an AI model (claude-sonnet-5-5) from the official reports in this thread; last updated . It may contain mistakes: the reports themselves are the authority.
GRB 261003A: Glowbug gamma-ray detection of a likely short burst