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A Spectacular Radio Flare from XRF 050416a at 40 Days and Implications for the Nature of X-Ray FlashesWe present detailed optical, near-infrared, and radio observations of the X-ray flash 050416a obtained with Palomar and Siding Springs Observatories as well as HST and the VLA, placing this event among the best-studied X-ray flashes to date. In addition, we present an optical spectrum from Keck LRIS from which we measure the redshift of the burst, Z=0.6528. At this redshift the isotropic-equivalent prompt energy release was about 10(exp 51) erg, and using a standard afterglow synchrotron model we find that the blastwave kinetic energy is a factor of 10 larger, E-K,iso approximately equals 10 (exp 52) erg. The lack of an observed jet break to t - 20 days indicates that the opening angle is larger than 7 deg and the total beaming-corrected relativistic energy is larger than 10 exp (50) erg. We further show that the burst produced a strong radio flare at t is similar to 40 days accompanied by an observed flattening in the X-ray band which we attribute to an abrupt circumburst density jump or an episode of energy injection (either from a refreshed shock or off-axis ejecta). Late-time observations with HST show evidence for an associated supernova with peak optical luminosity roughly comparable to that of SN 1998bw. Next, we show that the host galaxy of XRF 050416a is actively forming stars at a rate of at least 2 M-solar per year with a luminosity of L-B is similar to 0.5L* and metallicity of Z is similar to 0.2-0.8 Z-solar. Finally, we discuss the nature of XRF 050416a in the context of short-hard gamma-ray bursts and under the framework of off-axis and dirty fireball models for X-ray flashes.
Document ID
20090007965
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Soderberg, A. M.
(California Inst. of Tech. Pasadena, CA, United States)
Nakar, E.
(California Inst. of Tech. Pasadena, CA, United States)
Cenko, S. B.
(California Inst. of Tech. Pasadena, CA, United States)
Cameron, P. B.
(California Inst. of Tech. Pasadena, CA, United States)
Frail, D. A.
(National Radio Astronomy Observatory Socorro, NM, United States)
Kulkarni, S. R.
(California Inst. of Tech. Pasadena, CA, United States)
Fox, D. B.
(Pennsylvania State Univ. University Park, PA, United States)
Berger, E.
(Carnegie Institution of Washington Pasadena, CA, United States)
Gal-Yam, A.
(California Inst. of Tech. Pasadena, CA, United States)
Moon, D-S.
(California Inst. of Tech. Pasadena, CA, United States)
Price, P. A.
(Hawaii Univ. Honolulu, HI, United States)
Anderson, G.
(Australian National Univ. Weston Creek, Australia)
Schmidt, B. P.
(Australian National Univ. Weston Creek, Australia)
Salvo, M.
(Australian National Univ. Weston Creek, Australia)
Rich, J.
(Australian National Univ. Weston Creek, Australia)
Rau, A.
(California Inst. of Tech. Pasadena, CA, United States)
Ofek, E. O.
(California Inst. of Tech. Pasadena, CA, United States)
Chevalier, R. A.
(Virginia Univ. Charlottesville, VA, United States)
Hamuy, M.
(Carnegie Institution of Washington Pasadena, CA, United States)
Harrison, F. A.
(California Inst. of Tech. Pasadena, CA, United States)
Kumar, P.
(Texas Univ. Austin, TX, United States)
MacFadyen, A.
(Institute for Advanced Study Princeton, NJ, United States)
McCarthy, P. J.
(Carnegie Institution of Washington Washington, DC, United States)
Park, H. S.
(Lawrence Livermore National Lab. Livermore, CA, United States)
Peterson, B. A.
(Australian National Univ. Weston Creek, Australia)
Date Acquired
August 24, 2013
Publication Date
April 20, 2007
Publication Information
Publication: The Astrophysical Journal
Publisher: American Astronomical Society
Volume: 661
Subject Category
Astronomy
Funding Number(s)
CONTRACT_GRANT: NNG06GH61G
Distribution Limits
Public
Copyright
Other

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