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GRB 160625B: Evidence for a Gaussian-shaped Jet

Cunningham, V, Cenko, SB, Ryan, G, Vogel, SN, Corsi, A, Cucchiara, A, Fruchter, AS, Horesh, A, Kangas, T, Kocevski, D, Perley, DA and Racusin, J (2020) GRB 160625B: Evidence for a Gaussian-shaped Jet. Astrophysical Journal, 904 (2). ISSN 0004-637X

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Abstract

We present multiwavelength modeling of the afterglow from the long γ-ray burst (GRB) 160625B using Markov Chain Monte Carlo techniques of the afterglowpy Python package. GRB 160625B is an extremely bright burst with a rich set of observations spanning from radio to γ-ray frequencies. These observations range from ~0.1 days to >1000 days, thus making this event extremely well suited to such modeling. In this work we compare top-hat and Gaussian jet structure types in order to find best-fit values for the GRB jet collimation angle, viewing angle, and other physical parameters. We find that a Gaussian-shaped jet is preferred (2.7σ–5.3σ) over the traditional top-hat model. Our estimate for the opening angle of the burst ranges from 1fdg26 to 3fdg90, depending on jet-shape model. We also discuss the implications that assumptions on jet shape, viewing angle, and particularly the participation a fraction of electrons have on the final estimation of GRB intrinsic energy release and the resulting energy budget of the relativistic outflow. Most notably, allowing the participation fraction to vary results in an estimated total relativistic energy of ~1053 erg. This is two orders of magnitude higher than when the total fraction is assumed to be unity; thus, this parameter has strong relevance for placing constraints on long GRB central engines, details of the circumburst media, and host environment.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical and Space Sciences, 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics, 0306 Physical Chemistry (incl. Structural)
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: American Astronomical Society; IOP Publishing
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Date Deposited: 30 Mar 2021 11:33
Last Modified: 04 Sep 2021 05:40
DOI or Identification number: 10.3847/1538-4357/abc2cd
URI: https://researchonline.ljmu.ac.uk/id/eprint/14723

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