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Discovery of Radio Afterglow from the Most Distant Cosmic Explosion

Chandra, Poonam and Frail, Dale A. and Fox, Derek and Kulkarni, Shrinivas and Berger, Edo and Cenko, S. Bradley and Bock, Douglas C.-J. and Harrison, Fiona and Kasliwal, Mansi (2010) Discovery of Radio Afterglow from the Most Distant Cosmic Explosion. Astrophysical Journal Letters, 712 (1). L31-L35. ISSN 2041-8205. doi:10.1088/2041-8205/712/1/L31.

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We report on the discovery of radio afterglow emission from the gamma-ray burst GRB 090423, which exploded at a redshift of 8.3, making it the object with the highest known redshift in the universe. By combining our radio measurements with existing X-ray and infrared observations, we estimate the kinetic energy of the afterglow, the geometry of the outflow, and the density of the circumburst medium. Our best-fit model suggests a quasi-spherical, high-energy explosion in a low, constant-density medium. GRB 090423 had a similar energy release to the other well-studied high redshift GRB 050904 (z = 6.26), but their circumburst densities differ by 2 orders of magnitude. We compare the properties of GRB 090423 with a sample of gamma-ray bursts (GRBs) at moderate redshifts. We find that the high energy and afterglow properties of GRB 090423 are not sufficiently different from other GRBs to suggest a different kind of progenitor, such as a Population III (Pop III) star. However, we argue that it is not clear that the afterglow properties alone can provide convincing identification of Pop III progenitors. We suggest that the millimeter and centimeter radio detections of GRB 090423 at early times contained emission from the reverse shock. If true, this may have important implications for the detection of high-redshift GRBs by the next generation of radio facilities.

Item Type:Article
Related URLs:
URLURL TypeDescription
Fox, Derek0000-0002-3714-672X
Kulkarni, Shrinivas0000-0001-5390-8563
Berger, Edo0000-0002-9392-9681
Cenko, S. Bradley0000-0003-1673-970X
Harrison, Fiona0000-0003-2992-8024
Kasliwal, Mansi0000-0002-5619-4938
Additional Information:© 2010 American Astronomical Society. Received 2009 September 2, accepted for publication 2010 February 8. Published 2010 February 26. We thank the referee for useful comments. We thank Bob Dickman for allocation of VLA time and Joan Wrobel and Mark Claussen for scheduling the observations. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester. P.C. is supported by NSERC Discovery grants and DND-ARP grants held by Kristine Spekkens and Gregg Wade at RMC of Canada.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Department of National Defence (Canada & Australia)-Acid Rain ProgramUNSPECIFIED
UK Swift Science Data Centre, University of LeicesterUNSPECIFIED
Subject Keywords:cosmology: observations; gamma rays: bursts: general; hydrodynamics; radio continuum: general; stars: early-type
Issue or Number:1
Classification Code:PACS: 98.70.Rz; 97.20.Wt; 95.85.Nv; 97.10.Fy; 95.85.Bh; 95.85.Jq.
Record Number:CaltechAUTHORS:20100401-100722875
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17836
Deposited On:05 Apr 2010 20:58
Last Modified:08 Nov 2021 23:39

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