SubmilliJansky Transients in Archival Radio Observations - AstrophysicsReportar como inadecuado

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Abstract: ABRIDGED We report the results of a 944-epoch survey for transient sourceswith archival data from the Very Large Array spanning 22 years with a typicalepoch separation of 7 days. Observations were obtained at 5 or 8.4 GHz for asingle field of view with a full-width at half-maximum of 8.6- and 5.1-,respectively, and achieved a typical point-source detection threshold at thebeam center of ~300 microJy per epoch. Ten transient sources were detected witha significance threshold such that only one false positive would be expected.Of these transients, eight were detected in only a single epoch. Two transientswere too faint to be detected in individual epochs but were detected intwo-month averages. None of the ten transients was detected in longer-termaverages or associated with persistent emission in the deep image produced fromthe combination of all epochs. The cumulative rate for the short timescaleradio transients above 370 microJy at 5 and 8.4 GHz is 0.07 < R < 40 deg^-2yr^-1, where the uncertainty is due to the unknown duration of the transients,20 min < t char < 7 days. A two-epoch survey for transients will detect 1.5 +-0.4 transient per square degrees above a flux density of 370 microJy. Twotransients are associated with galaxies at z=0.040 and z=0.249. These may besimilar to the peculiar Type Ib-c radio supernova SN 1998bw associated with GRB980428. Six transients have no counterparts in the optical or infrared (R=27,Ks=18). The hosts and progenitors of these transients are unknown.

Autor: Geoffrey C. Bower, Destry Saul, Joshua S. Bloom, Alberto Bolatto, Alexei V. Filippenko, Ryan J. Foley, Daniel Perley (UC Berkeley)


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