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GCN Circular 35196

Subject
GRB 231125A (short): Glowbug gamma-ray detection
Date
2023-11-27T01:19:23Z (3 months ago)
From
C.C. Cheung at Naval Research Lab <Teddy.Cheung@nrl.navy.mil>
Via
Web form
C.C. Cheung, M. Kerr, J. E. Grove, R. Woolf (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge (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 231125A, which was also detected by Astrosat/CZTI and INTEGRAL/SPI-ACS (GCN 35190).

Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2023-11-25 17:47:19.344 with a duration of 1.15 s and a total significance of about 194 sigma.  The light curve comprises a single peak.

Using a standard power-law function with an exponential high-energy cutoff [3] to model the emission over this duration results in a photon index dN/dE~E^x of x=0.7 and a cutoff energy ("Epeak") of 296 keV.  The modeled 10-10000 keV fluence is 6.1e-06 erg/cm^2.

The best-fit localization is RA, Decl. (J2000) = 109.7 deg, -30.6 deg with a radius of 2.6 deg (95% confidence), with a highly uncertain systematic uncertainty.

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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