TITLE: GCN CIRCULAR NUMBER: 42151 SUBJECT: GRB 251007A: Glowbug gamma-ray detection DATE: 25/10/07 22:35:45 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung@nrl.navy.mil> 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 251007A, which was also detected by Swift/BAT (GCN 42146) and CALET (Trigger 1443900615). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-10-07 19:37:09.088 with a duration of 65.5 s and a total significance of about 137.8 sigma. The Glowbug light curve is dominated by a triple-peaked structure spanning ~ T0+40s to +60s corresponding to the peak emission observed by Swift/BAT and CALET. Note the Glowbug onset time is ~11 s after the Swift/BAT trigger time (19:36:58). A search of the Glowbug data for emission at the Swift/BAT T0 was inconclusive. 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 recently 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/42151. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...