Chandra 2009 GRB 090423的射电余辉观测

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Title:		Discovery of Radio Afterglow from the Most Distant Cosmic Explosion
Authors:		Chandra, Poonam; Frail, Dale A.; Fox, Derek; Kulkarni, Shrinivas; Berger, Edo; Cenko, S. Bradley; Bock, Douglas C.-J.; Harrsion, Fiona; Kasliwal, Mansi
Affiliation:		AA(Department of Physics, Royal Military College of Canada, Kingston, ON, Canada poonam.chandra@rmc.ca), AB(National Radio Astronomy Observatory, 1003 Lopezville Road, Socorro, NM 87801, USA ), AC(Department of Astronomy and Astrophysics, 525 Davey Laboratory, Pennsylvania State University, University Park, PA 16802, USA ), AD(Department of Astronomy, California Institute of Technology, Pasadena, CA 91125, USA ), AE(Harvard University, 60 Garden Street, Cambridge, MA 02138, USA ), AF(Department of Astronomy, 601 Campbell Hall, University of California, Berkeley, CA 94720-3411, USA ), AG(Combined Array for Research in Millimeter-wave Astronomy, P.O. Box 968, Big Pine, CA 93513, USA), AH(Department of Astronomy, California Institute of Technology, Pasadena, CA 91125, USA ), AI(Department of Astronomy, California Institute of Technology, Pasadena, CA 91125, USA )
Publication:		The Astrophysical Journal Letters, Volume 712, Issue 1, pp. L31-L35 (2010). (ApJL Homepage)
Publication Date:		03/2010
Origin:		IOP
ApJ Keywords:		cosmology: observations, gamma-ray burst: general, hydrodynamics, radio continuum: general, stars: early-type
DOI:		10.1088/2041-8205/712/1/L31
Bibliographic Code:		2010ApJ...712L..31C

Abstract

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.

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