A REVERSE SHOCK in GRB 160509A

Tanmoy Laskar, Kate D. Alexander, Edo Berger, Wen Fai Fong, Raffaella Margutti, Isaac Shivvers, Peter K.G. Williams, Drejc Kopač, Shiho Kobayashi, Carole Mundell, Andreja Gomboc, Weikang Zheng, Karl M. Menten, Melissa L. Graham, Alexei V. Filippenko

Research output: Contribution to journalArticlepeer-review

64 Scopus citations

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.

Original languageEnglish (US)
Article number88
JournalAstrophysical Journal
Volume833
Issue number1
DOIs
StatePublished - Dec 10 2016

Funding

This work was supported in part by the NSF under grant No. PHYS-1066293; A.V.F. thanks the Aspen Center for Physics for its hospitality during the black holes workshop in 2016 June. This research has made use of data obtained through the High Energy Astrophysics Science Archive Research Center Online Service, provided by the NASA/Goddard Space Flight Center. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration, and was made possible by the generous financial support of the W.M. Keck Foundation. VLA observations were taken as part of our VLA Large Program 15A-235 (PI: E. Berger). The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Keywords

  • gamma-ray burst: general
  • gamma-ray burst: individual (GRB 160509A) Supporting material: machine-readable table

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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