Article

A Redshift Determination for XRF 020903: First Spectroscopic Observations of an X‐Ray Flash

A. M. SoderbergDivision of Physics, Mathematics, and Astronomy, MS 105-24, California Institute of Technology, Pasadena, CA 91125S. R. KulkarniDivision of Physics, Mathematics, and Astronomy, MS 105-24, California Institute of Technology, Pasadena, CA 91125E. BergerDivision of Physics, Mathematics, and Astronomy, MS 105-24, California Institute of Technology, Pasadena, CA 91125D. B. FoxDivision of Physics, Mathematics, and Astronomy, MS 105-24, California Institute of Technology, Pasadena, CA 91125P. A. PriceDivision of Physics, Mathematics, and Astronomy, MS 105-24, California Institute of Technology, Pasadena, CA 91125S. A. YostDivision of Physics, Mathematics, and Astronomy, MS 105-24, California Institute of Technology, Pasadena, CA 91125Matthew P. HuntDivision of Physics, Mathematics, and Astronomy, MS 105-24, California Institute of Technology, Pasadena, CA 91125D. A. FrailNational Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801R. C. WalkerNational Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801M. HamuyCarnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101Stephen A. ShectmanCarnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101J. P. HalpernAstronomy Department, Mail Code 5246, Columbia University, New York, NY 10027N. MirabalAstronomy Department, Mail Code 5246, Columbia University, New York, NY 10027

2004en

ABI

Abstract

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. Moreover, XRF 020903 is the first X-ray flash for which we detect an optical afterglow. The luminosity of the radio afterglow of XRF 020903 is 1000 times greater than that of Ibc supernovae but similar to those of GRB afterglows. From broadband afterglow modeling we show that the explosion 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.

Identifiers

DOI: 10.1086/383082

Citations and references

Cited by 20 references

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