GCN Circular 35897
Subject
GRB 240229A: Glowbug gamma-ray detection
Date
2024-03-07T14:43:24Z (2 months ago)
From
C.C. Cheung at Naval Research Lab <Teddy.Cheung@nrl.navy.mil>
Via
Web form
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], operating on the International Space Station, reports the detection of GRB 240229A, which was also detected by Fermi/GBM (GCN 35833, 35834), CALET (GCN 35842), INTEGRAL/SPI-ACS, Konus/Wind, BepiColombo (GCN 35870), VZLUSAT-2 (GCN 35872), and GRBAlpha (GCN 35894).
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2024-02-29 14:07:09.552 with a duration of 24.6 s and a total significance of about 27.0 sigma. The light curve comprises two primary peaks at ~T0+3s and ~T0+23s.
Using a standard power-law function with an exponential high-energy cutoff [3] to model the emission in two defined intervals from T0 to T0+10.2s and T0+20.5s to +24.6s resulted respectively in photon indices dN/dE~E^x of x=0.5 and x=1.5, and cutoff energies ("Epeak") of 728 keV and 439 keV. The respective modeled 10-10000 keV fluences are 3.9e-06 erg/cm^2 and 9.6e-07 erg/cm^2.
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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