TITLE: GCN CIRCULAR NUMBER: 43133 SUBJECT: GRB 251215A: Glowbug gamma-ray detection DATE: 25/12/15 23:10:15 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 251215A, which was also detected by Fermi/GBM (GCN 43104), Swift/BAT-GUANO (GCN 43114), and CALET (trigger 1449807236). Glowbug was in the SAA at the time of the GBM T0 (04:21:21) and recorded data beginning at T0+20s, initially with high background rates as it was exiting the SAA. Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-12-15 04:22:25.800 with a duration of 76.0 s and a total significance of about 23.8 sigma. The burst originated toward the Nadir side of Glowbug and was detected despite passing through the passive material from the H9 pallet and internal passive material/shielding within Glowbug. The Glowbug onset is 64.8 s after the GBM T0, and the Glowbug light curve comprises three peaks at ~T0+1s, ~T0+25s, and ~T0+72s; the T0+72s peak matches the CALET trigger time (04:23:36.282). 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 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/43133. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...