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On the Origin of the Multi-GeV Photons from the Closest Burst with Intermediate Luminosity: GRB 190829A

Fraija, N. and Veres, P. and Beniamini, P. and Galvan-Gamez, A. and Metzger, B. D. and Barniol Duran, R. and Becerra, R. L. (2021) On the Origin of the Multi-GeV Photons from the Closest Burst with Intermediate Luminosity: GRB 190829A. Astrophysical Journal, 918 (1). Art. No. 12. ISSN 0004-637X. doi:10.3847/1538-4357/ac0aed.

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Very high energy (VHE) emission is usually interpreted in the synchrotron self-Compton scenario and expected from the low-redshift and high-luminosity gamma-ray bursts (GRBs), such as GRB 180720B and GRB 190114C. Recently, the H.E.S.S. telescopes reported VHE emission from one of the closest bursts, GRB 190829A, which was associated with the supernova 2019oyw. In this paper, we present a temporal and spectral analysis from optical bands to the Fermi-LAT energy range over multiple observational periods beginning after the trigger time and extending for almost 3 months. We show that the X-ray and optical observations are consistent with synchrotron forward-shock emission evolving between the characteristic and cooling spectral breaks during the early and late afterglow in a uniform-density medium. Modeling the light curves together with the spectral energy distribution, we show that the outflow expanded with an initial bulk Lorentz factor of Γ ∼ 30, which is high for low-luminosity GRBs and low for high-luminosity GRBs. The values of the initial bulk Lorentz factor and the isotropic-equivalent energy suggest that GRB 190829A is an intermediate-luminosity burst; consequently, it becomes the first burst of this class to be detected in the VHE gamma-ray band by an imaging atmospheric Cherenkov telescope and, in turn, the first event to not be simultaneously observed by the Fermi-LAT instrument. Analyzing the intermediate-luminosity bursts with z ≲ 0.2, such as GRB 130702A, we show that bursts with intermediate luminosities are potential candidates to be detected in VHEs.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Fraija, N.0000-0002-0173-6453
Veres, P.0000-0002-2149-9846
Beniamini, P.0000-0001-7833-1043
Galvan-Gamez, A.0000-0001-5193-3693
Metzger, B. D.0000-0002-4670-7509
Barniol Duran, R.0000-0002-5565-4824
Becerra, R. L.0000-0002-0216-3415
Additional Information:© 2021. The American Astronomical Society. Received 2020 March 29; revised 2021 April 25; accepted 2021 June 12; published 2021 August 30. N.F. acknowledges financial support from UNAM-DGAPA-PAPIIT through grant IN106521. R.B.D. acknowledges support from the National Science Foundation under grant 1816694.
Funding AgencyGrant Number
Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica (PAPIIT)IN106521
Subject Keywords:High energy astrophysics
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: High energy astrophysics (739)
Record Number:CaltechAUTHORS:20210914-225403666
Persistent URL:
Official Citation:N. Fraija et al 2021 ApJ 918 12
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110896
Deposited By: George Porter
Deposited On:16 Sep 2021 21:35
Last Modified:16 Sep 2021 21:35

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