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Evidence for supernova-synthesized dust from the rising afterglow of GRB 071025 at z ∼ 5

Perley, DA and Bloom, JS and Klein, CR and Covino, S and Minezaki, T and Woźniak, P and Vestrand, WT and Williams, GG and Milne, P and Butler, NR and Updike, AC and Krühler, T and Afonso, P and Antonelli, A and Cowie, L and Ferrero, P and Greiner, J and Hartmann, DH and Kakazu, Y and Küpcü Yoldaş, A and Morgan, AN and Price, PA and Prochaska, JX and Yoshii, Y (2010) Evidence for supernova-synthesized dust from the rising afterglow of GRB 071025 at z ∼ 5. Monthly Notices of the Royal Astronomical Society, 406 (4). pp. 2473-2487. ISSN 0035-8711

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Abstract

We present observations and analysis of the broad-band afterglow of Swift GRB 071025. Using optical and infrared (RIYJHK) photometry, we derive a photometric redshift of 4.4 < z < 5.2; at this redshift our simultaneous multicolour observations begin at ∼30 s after the gamma-ray burst trigger in the host frame, during the initial rising phase of the afterglow. We associate the light-curve peak at ∼580 s in the observer frame with the formation of the forward shock, giving an estimate of the initial Lorentz factor Γ0 ∼ 200. The red spectral energy distribution (even in regions not affected by the Lyman α break) provides secure evidence of a large dust column. However, the inferred extinction curve shows a prominent flat component between 2000 and 3000 Å in the rest frame, inconsistent with any locally observed template but well fitted by models of dust formed by supernovae. Time-dependent fits to the extinction profile reveal no evidence of dust destruction and limit the decrease in the extinction column to ΔA3000 < 0.54 mag after t = 50 s in the rest frame. Together with studies of high-z quasars, our observations suggest a transition in dust properties in the early Universe, possibly associated with a transition between supernova-dominated and asymptotic giant branch-dominated modes of dust production. © 2010 The Authors. Journal compilation © 2010 RAS.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2010 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
Date Deposited: 18 May 2017 10:57
Last Modified: 18 May 2017 10:57
DOI or Identification number: 10.1111/j.1365-2966.2010.16772.x
URI: http://researchonline.ljmu.ac.uk/id/eprint/6483

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