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GRB 071003: Broadband Follow-up Observations of a Very Bright Gamma-Ray Burst in a Galactic Halo

Perley, D. A. and Li, W. and Chornock, R. and Prochaska, J. X. and Butler, N. R. and Chandra, P. and Pollack, L. K. and Bloom, J. S. and Filippenko, A. V. and Swan, H. and Yuan, F. and Akerlof, C. and Auger, M. W. and Cenko, S. B. and Chen, H.-W. and Fassnacht, C. D. and Fox, D. and Frail, D. and Johansson, E. M. and McKay, T. and Le Mignant, D. and Modjaz, M. and Rujopakarn, W. and Russel, R. and Skinner, M. A. and Smith, G. H. and Smith, I. and van Dam, M. A. and Yost, S. (2008) GRB 071003: Broadband Follow-up Observations of a Very Bright Gamma-Ray Burst in a Galactic Halo. Astrophysical Journal, 688 (1). pp. 470-490. ISSN 0004-637X. doi:10.1086/591961.

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The optical afterglow of long-duration GRB 071003 is among the brightest yet to be detected from any GRB, with R ≈ 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 II 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 II for GRB redshift determination. We present early- through late-time observations spanning the electromagnetic 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.

Item Type:Article
Related URLs:
URLURL TypeDescription
Perley, D. A.0000-0001-8472-1996
Chornock, R.0000-0002-7706-5668
Prochaska, J. X.0000-0002-7738-6875
Bloom, J. S.0000-0002-7777-216X
Filippenko, A. V.0000-0003-3460-0103
Cenko, S. B.0000-0003-1673-970X
Fassnacht, C. D.0000-0002-4030-5461
Fox, D.0000-0002-3714-672X
Modjaz, M.0000-0001-7132-0333
Additional Information:© 2008 The American Astronomical Society. Received 2008 May 15; accepted 2008 July 15. This research is based in part on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership. 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 NASA; the Observatory was made possible by the generous financial support of the W. M. Keck Foundation. We wish to extend special thanks to those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests. We are grateful to the staffs at the Gemini, Keck, and Lick Observatories for their assistance.
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:gamma rays: bursts
Issue or Number:1
Record Number:CaltechAUTHORS:20090407-082512222
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13860
Deposited By: Tony Diaz
Deposited On:15 Jul 2009 21:13
Last Modified:08 Nov 2021 22:41

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