TITLE: GCN CIRCULAR NUMBER: 44757 SUBJECT: GRB 260527A/EP260527a: Glowbug gamma-ray detection DATE: 26/06/01 12:58:49 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung@nrl.navy.mil> The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 260527A, which was detected initially by Einstein Probe as EP260527a (GCN 44718). The GRB was also detected by Konus-Wind (GCN 44722), GECAM-B (GCN 44724), CALET (GCN 44726), Insight-HXMT (GCN 44735), and Mars-Odyssey (HEND) with an IPN triangulation (GCN 44744). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-05-27 06:16:08.912 with a duration of 0.26 s and a total significance of about 40 sigma. The light curve comprises a primary peak at ~T0+0.1s and a fainter peak at ~T0+0.2s. 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/44757. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...