{
  "body": "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:\n \nThe Glowbug gamma-ray telescope [1,2], operating on the International Space Station, reports the detection of GRB 240421A, which was also detected by Fermi/GBM (GCN 36204).\n \nUsing an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2024-04-21 05:21:56.632 with a duration of 2.0 s and a total significance of about 11.3 sigma.  The light curve comprises a double-peaked structure.\n \nThe analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS.\n \nGlowbug 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.\n \n[1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959\n[2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O\n[3] Goldstein, A. et al. 2020, ApJ 895, 40, arXiv :1909.03006\n \nDistribution Statement A: Approved for public release.  Distribution is unlimited.",
  "eventId": "GRB 240421A",
  "createdOn": 1713809371436,
  "submittedHow": "web",
  "submitter": "C.C. Cheung at Naval Research Lab <Teddy.Cheung@nrl.navy.mil>",
  "subject": "GRB 240421A: Glowbug gamma-ray detection",
  "bibcode": "2024GCN.36232....1C",
  "circularId": 36232
}