TITLE: GCN CIRCULAR NUMBER: 44559 SUBJECT: GRB 260506B: Glowbug gamma-ray detection DATE: 26/05/11 17:12:04 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 260506B, which was also detected by Fermi/GBM (GCN 44484, 44485) and AstroSat/CZTI (GCN 44503). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-05-06 13:07:30.824 with a duration of 20.5 s and a total significance of about 34 sigma. The lightcurve comprises a faint initial peak at ~T0+1s, a complex structure from ~T0+7s to +15s, and a peak at ~T0+21s — the peaks correspond to the brightest features seen in the GBM lightcurve. Note that data from ~T0-1s to +1s 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 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/44559. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...