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GCN Circular 35161

Subject
GRB 231122B: Glowbug gamma-ray detection
Date
2023-11-22T21:21:17Z (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 231122B, which was also detected by GECAM-B (GCN 35157) and CALET/GBM (trigger ID Num 1384701074).

Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2023-11-22 15:12:34.760 with a duration of 41.0 s and a total significance of about 55.7 sigma.  The light curve comprises an initial peak at ~T0+5s followed by a multi-peaked structure with a maximum rate at ~T0+35s.

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=0.9 and a cutoff energy ("Epeak") of 308 keV.  The modeled 10-10000 keV fluence is 9.7e-06 erg/cm^2.

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=0.2 and a cutoff energy ("Epeak") of 461 keV.  The modeled 10-10000 keV fluence is 5.1e-06 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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