TITLE: GCN CIRCULAR NUMBER: 44312 SUBJECT: GRB 260411B: Glowbug gamma-ray detection DATE: 26/04/16 13:36:13 GMT FROM: Richard S. Woolf at US Naval Research Laboratory <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 260411B, which was also detected by Fermi GBM (GCN 44262, 44266), SVOM/GRM (GCN 44268), Fermi LAT (GCN 44277), and GECAM (GCN 44285). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-04-11 08:04:43.568 with a duration of 3.1 s and a total significance of about 22.6 sigma. At the time of the detection, the ISS was entering a high background region and Glowbug captured the second, brighter peak visible in the GBM lightcurve. The initial, fainter peak near the GBM T0 may be detected by Glowbug at low significance. 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/44312. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...