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Evidence for dust destruction from the early-time colour change of GRB 120119A

Morgan, AN and Perley, DA and Cenko, SB and Bloom, JS and Cucchiara, A and Richards, JW and Filippenko, AV and Haislip, JB and LaCluyze, A and Corsi, A and Melandri, A and Cobb, BE and Gomboc, A and Horesh, A and James, B and Li, W and Mundell, CG and Reichart, DE and Steele, IA (2014) Evidence for dust destruction from the early-time colour change of GRB 120119A. Monthly Notices of the Royal Astronomical Society, 440 (2). pp. 1810-1823. ISSN 0035-8711

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Abstract

We present broad-band observations and analysis of Swift gamma-ray burst (GRB) 120119A. Our early-time afterglow detections began under 15 s after the burst in the host frame (redshift z = 1.73), and they yield constraints on the burst energetics and local environment. Late-time afterglow observations of the burst show evidence for a moderate column of dust (AV ≈ 1.1 mag) similar to, but statistically distinct from, dust seen along Small Magellanic Cloud sightlines. Deep late-time observations reveal a dusty, rapidly star-forming host galaxy. Most notably, our early-time observations exhibit a significant red-to-blue colour change in the first ∼200 s after the trigger at levels heretofore unseen in GRB afterglows. This colour change, which is coincident with the final phases of the prompt emission, is a hallmark prediction of the photodestruction of dust in GRB afterglows. We test whether dust-destruction signatures are significantly distinct from other sources of colour change, namely a change in the intrinsic spectral index β. We find that a time-varying power-law spectrum alone cannot adequately describe the observed colour change, and allowing for dust destruction (via a time-varying AV) significantly improves the fit. While not definitively ruling out other possibilities, this event provides the best support yet for the direct detection of dust destruction in the local environment of a GRB.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: 0201 Astronomical And Space Sciences
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press
Related URLs:
Date Deposited: 23 May 2017 12:12
Last Modified: 06 Sep 2017 19:04
DOI or Identification number: 10.1093/mnras/stu344
URI: http://researchonline.ljmu.ac.uk/id/eprint/6555

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