The first two host galaxies of X-ray flashes: XRF 011030 and XRF 020427

J. S. Bloom, D. Fox, P. G. Van Dokkum, S. R. Kulkarni, E. Berger, S. G. Djorgovski, D. A. Frail

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


Given the paucity of empirical constraints, the nature of the newly recognized phenomena called X-ray flashes (XRFs) has been an open question. However, with the recent detections of radio and X-ray afterglow it is finally possible to study the large- and small-scale environments of XRFs. We present Chandra, Hubble Space Telescope (HST), and Keck observations of the fields of XRFs 011030 and 020427. Astrometric comparisons of the X-ray transient positions and the HST images reveal the XRFs to be associated with faint blue galaxies. Photometric evidence of these putative hosts suggests that these two XRFs originated from redshifts less than z ∼ 3.5, and thus cannot be due to GRBs at very high redshifts. In both host-burst offsets and host properties, these XRFs could have been drawn from distributions similar to those measured of gamma-ray bursts (GRBs). We conclude with a discussion of the implications of this XRF-GRB host connection for the possible progenitors of XRFs.

Original languageEnglish (US)
Pages (from-to)957-963
Number of pages7
JournalAstrophysical Journal
Issue number2 I
StatePublished - Dec 20 2003

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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