AAS 203rd Meeting, January 2004
Session 132 Gamma Ray Bursts: Processes and Phenomena
Oral, Thursday, January 8, 2004, 2:00-3:30pm, Centennial IV

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[132.07] A Redshift Determination for XRF 020903: First Spectroscopic Observations of an X-Ray Flash

A. M. Soderberg (California Institute of Technology)

We report the discovery of optical and radio afterglow emission from the extremely soft X-ray flash, XRF 020903. Our spectroscopic observations provide the first redshift for an X-ray flash, thereby setting the distance scale for these events. At z=0.251, XRF 020903 is one of the nearest cosmic explosions ever detected, second only to the recent GRB 030329 and the unusual GRB 980425/SN 1998bw. Finally, XRF 020903 is the first X-ray flash for which we detect an optical afterglow coincident with a bright radio counterpart. The temporal evolution of the radio flux density (t=30-300 days) clearly distinguishes the transient source as an afterglow. From broadband afterglow modeling we show that the relativistic energy of XRF 020903 is not dissimilar from values inferred for typical gamma-ray bursts, suggesting that these cosmological explosions may derive from a similar mechanism.

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The author(s) of this abstract have provided an email address for comments about the abstract: ams@astro.caltech.edu

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.