TITLE: GCN CIRCULAR NUMBER: 45749 SUBJECT: GRB 260923A: Glowbug gamma-ray detection DATE: 26/09/25 18:07:16 GMT FROM: C.C. Cheung at Naval Research Lab 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 260923A, which was also detected by Fermi/GBM (GCN 45710) and Insight-HXMT/HE (GCN 45738). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-09-23 23:41:32.368 with a duration of 88.3 s and a total significance of about 93.3 sigma. The light curve comprises a complex multi-peaked structure.  Note that data from throughout the burst interval 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.   [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.