A Revised View of the Transient Radio Sky
  We report on a re-analysis of archival data from the Very Large Array for a
sample of ten long duration radio transients reported by Bower and others.
These transients have an implied all-sky rate that would make them the most
common radio transient in the sky and yet most have no quiescent counterparts
at other wavelengths and therefore no known progenitor (other than Galactic
neutron stars). We find that more than half of these transients are due to rare
data artifacts. The remaining sources have lower signal-to-noise ratio (SNR)
than initially reported by 1 to 1.5-sigma. This lowering of SNR matters greatly
since the sources are at the threshold. We are unable to decisively account for
the differences. By two orthogonal criteria one source appears to be a good
detection. Thus the rate of long duration radio transients without optical
counterparts is, at best, comparable to that of the class of recently
discovered Swift J1644+57 nuclear radio transients. We revisit the known and
expected classes of long duration radio transients and conclude that the
dynamic radio sky remains a rich area for further exploration. Informed by the
experience of past searches for radio transients, we suggest that future
surveys pay closer attention to rare data errors and ensure that a wealth of
sensitive multi-wavelength data be available in advance of the radio
observations and that the radio searches should have assured follow-up
resources.
