A. J. Stewart et al., "LOFAR MSSS: detection of a low-frequency
radio transient in 400 h of monitoring of the North Celestial
Pole," Monthly Notices of the Royal Astronomical Society, V456,
no. 3, pp2321-2342, March 2016.
abstract:
We present the results of a four-month campaign searching for
low-frequency radio transients near the North Celestial Pole with the
Low-Frequency Array (LOFAR), as part of the Multifrequency Snapshot
Sky Survey (MSSS). The data were recorded between 2011 December and
2012 April and comprised 2149 11-minute snapshots, each covering 175
deg2. We have found one convincing candidate astrophysical
transient, with a duration of a few minutes and a flux density at 60
MHz of 15-25 Jy. The transient does not repeat and has no obvious
optical or high-energy counterpart, as a result of which its nature is
unclear. The detection of this event implies a transient rate at 60
MHz of 3.9-3.7+14.7 10-4
day-1 deg-2, and a transient surface
density of 1.5 10-5 deg-2, at a 7.9-Jy limiting
flux density and ~10-minute time-scale. The campaign data were also
searched for transients at a range of other time-scales, from 0.5 to
297 min, which allowed us to place a range of limits on transient
rates at 60 MHz as a function of observation duration.
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