TITLE: GCN CIRCULAR NUMBER: 36290 SUBJECT: GRB 240422A: Glowbug gamma-ray detection DATE: 24/04/24 21:13:46 GMT FROM: C.C. Cheung at Naval Research Lab Teddy.Cheung@nrl.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], operating on the International Space Station, reports the detection of GRB 240422A, which was also detected by Fermi/GBM (GCN 36222).
The detection occurred during a time of high background, thus complicating the analysis. Using an adaptive window with a resolution of 32-ms, the initial peak seen in the GBM light curve was recovered, with a burst onset determined to be 2024-04-22 02:40:55.400 with a duration of 4.1 s and a total significance of about 8.0 sigma.
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. The detector comprises 12 large-area (15 cm x 15 cm) CsI:Tl panels covering the surface of a half cube, and two hexagonal (5-cm diameter, 10-cm length) CLLB scintillators, giving it a large field of view (instantaneous FoV ~2/3 sky) over a wide energy band of 50 keV to >2 MeV.
[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] Goldstein, A. et al. 2020, ApJ 895, 40, arXiv :1909.03006
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