TITLE: GCN CIRCULAR NUMBER: 42490 SUBJECT: GRB 251025C: Glowbug gamma-ray detection DATE: 25/10/27 19:37:00 GMT FROM: richard.s.woolf.civ@us.navy.mil
R. Woolf, C.C. Cheung, 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 251025C, which was also detected by Fermi GBM (GCN 42449), CALET (GCN 42467), and AstroSat CZTI (GCN 42469).
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-10-25 23:08:38.104 with a duration of 22.5 s and a total significance of about 46.8 sigma. The light curve comprises an initial fast rise/decay component in the T0 to T0+5s window, followed by secondary emission with slow exponential decay extending to T0+22.5s. Note that data from ~T0 to T0+1.5s and ~T0+3s to T0+5.5s suffered from deadtime in various detectors.
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
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