Laskar, T, Alexander, KD, Berger, E, Fong, WF, Margutti, R, Shivvers, I, Williams, PKG, Kopač, D, Kobayashi, S, Mundell, C, Gomboc, A, Zheng, W, Menten, KM, Graham, ML and Filippenko, AV (2016) A REVERSE SHOCK in GRB 160509A. Astrophysical Journal, 833 (1). ISSN 0004-637X

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Abstract

We present the second multi-frequency radio detection of a reverse shock in a γ-ray burst. By combining our extensive radio observations of the Fermi-Large Area Telescope γ-ray burst 160509A at z = 1.17 up to 20 days after the burst with Swift X-ray observations and ground-based optical and near-infrared data, we show that the afterglow emission comprises distinct reverse shock and forward shock contributions: the reverse shock emission dominates in the radio band at ≲10 days, while the forward shock emission dominates in the X-ray, optical, and near-infrared bands. Through multi-wavelength modeling, we determine a circumburst density of , supporting our previous suggestion that a low-density circumburst environment is conducive to the production of long-lasting reverse shock radiation in the radio band. We infer the presence of a large excess X-ray absorption column, N H ≈ 1.5 ×1022 , and a high rest-frame optical extinction, A V ≈ 3.4 mag. We identify a jet break in the X-ray light curve at , and thus derive a jet opening angle of , yielding a beaming-corrected kinetic energy and radiated γ-ray energy of erg and erg (1-104 keV, rest frame), respectively. Consistency arguments connecting the forward shocks and reverse shocks suggest a deceleration time of s ≈ T 90, a Lorentz factor of , and a reverse-shock-to-forward-shock fractional magnetic energy density ratio of . Our study highlights the power of rapid-response radio observations in the study of the properties and dynamics of γ-ray burst ejecta. © 2016. The American Astronomical Society. All rights reserved.

Item Type:	Article
Uncontrolled Keywords:	0201 Astronomical And Space Sciences, 0305 Organic Chemistry, 0306 Physical Chemistry (Incl. Structural)
Subjects:	Q Science > QB Astronomy Q Science > QC Physics Q Science > QD Chemistry
Divisions:	Astrophysics Research Institute
Publisher:	American Astronomical Society
Date Deposited:	09 Jan 2017 12:10
Last Modified:	04 Sep 2021 12:08
DOI or ID number:	10.3847/1538-4357/833/1/88
URI:	https://researchonline.ljmu.ac.uk/id/eprint/5204

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