DISCOVERY OF RADIO AFTERGLOW FROM THE MOST DISTANT COSMIC EXPLOSION
- Department of Physics, Royal Military College of Canada, Kingston, ON (Canada)
- National Radio Astronomy Observatory, 1003 Lopezville Road, Socorro, NM 87801 (United States)
- Department of Astronomy and Astrophysics, 525 Davey Laboratory, Pennsylvania State University, University Park, PA 16802 (United States)
- Department of Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)
- Harvard University, 60 Garden Street, Cambridge, MA 02138 (United States)
- Department of Astronomy, 601 Campbell Hall, University of California, Berkeley, CA 94720-3411 (United States)
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.
- OSTI ID:
- 21305092
- Journal Information:
- Astrophysical Journal Letters, Vol. 712, Issue 1; Other Information: DOI: 10.1088/2041-8205/712/1/L31; Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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