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GRB 071003: Broadband follow-up observations of a very bright gamma-ray burst in a galactic halo

Perley, DA and Li, W and Chornock, R and Prochaska, JX and Butler, NR and Chandra, P and Pollack, LK and Bloom, JS and Fllippenko, AV and Swan, H and Yuan, F and Akerlof, C and Auger, MW and Cenko, SB and Chen, HW and Fassnacht, CD and Fox, D and Frail, D and Johansson, EM and McKay, T and Le Mignant, D and Modjaz, M and Rujopakarn, W and Russel, R and Skinner, MA and Smith, GH and Smith, I and Van Dam, MA and Yost, S (2008) GRB 071003: Broadband follow-up observations of a very bright gamma-ray burst in a galactic halo. The Astrophysical Journal, 688 (1). pp. 470-490. ISSN 1538-4357

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Abstract

The optical afterglow of long-duration GRB 071003 is among the brightest yet to be detected from any GRB, with A ≈ 12 mag in KAIT observations starting 42 s after the GRB trigger, including filtered detections during prompt emission. However, our high-S/N afterglow spectrum displays only extremely weak absorption lines at what we argue is the host redshift of z = 1.60435, in contrast to the three other, much stronger Mg IT absorption systems observed at lower redshifts. Together with Keck adaptive optics observations, which fail to reveal a host galaxy coincident with the burst position, our observations suggest a halo progenitor and offer a cautionary tale about the use of Mg n for GRB redshift determination. We present early- through late-time observations spanning the electro-magnetic spectrum, constrain the connection between the prompt emission and early variations in the light curve (we observe no correlation), and discuss possible origins for an unusual, marked rebrightening that occurs a few hours after the burst: likely either a late-time refreshed shock or a wide-angle secondary jet. Analysis of the late-time afterglow is most consistent with a wind environment, suggesting a massive star progenitor. Together with GRB 070125, this may indicate that a small but significant portion of star formation in the early universe occurred far outside what we consider a normal galactic disk. © 2008. 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: 23 May 2017 10:14
Last Modified: 23 May 2017 10:14
DOI or Identification number: 10.1086/591961
URI: http://researchonline.ljmu.ac.uk/id/eprint/6505

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