Submillijansky transients in archival radio observations

Geoffrey C. Bower, Destry Saul, Joshua S. Bloom, Alberto Bolatto, Alexei V. Filippenko, Ryan J. Foley, Daniel Perley

Research output: Contribution to journalArticlepeer-review

Abstract

We report the results of a 944 epoch survey for transient sources with archival data from the Very Large Array spanning 22 years with a typical epoch separation of 7 days. Observations were obtained at 5 or 8.4 GHz for a single field of view and achieved a typical point-source detection threshold at the beam center of 300 μJy per epoch. Ten transient sources were detected with a significance threshold such that only one false positive would be expected. Of these transients, eight were detected in only a single epoch. Two transients were too faint to be detected in individual epochs but were detected in 2 month averages. None of the 10 transients was detected in longer term averages or associated with persistent emission in the deep image produced from the combination of all epochs. The cumulative rate for the short-timescale radio transients above 370 μJy at 5 and 8.4 GHz is 0.07 deg-2 yr -1 ≲ R ≲ 40 deg-2 yr-1, where the uncertainty is due to the unknown duration of the transients, 20 minutes < tchar < 7 days. A two-epoch survey for transients will detect 1.5 ± 0.4 transients per square degree above a flux density of 3 70 μJy. Two transients are associated with galaxies at z = 0.040 and z = 0.249. These may be similar to the peculiar Type Ib/c radio supernova SN 1998bw associated with GRB 980428. We detect no counterparts for six transients in deep optical and infrared imaging. The hosts and progenitors of these transients are unknown.

Original languageEnglish (US)
Pages (from-to)346-360
Number of pages15
JournalAstrophysical Journal
Volume666
Issue number1 I
DOIs
StatePublished - 2007

Keywords

  • Gamma rays: bursts
  • Radio continuum: general
  • Radio continuum: stars
  • Supernovae: general
  • Surveys

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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