LOFAR MSSS: detection of a low-frequency radio transient in 400 h of monitoring of the North Celestial Pole
Artikel i vetenskaplig tidskrift, 2016
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-min snapshots, each covering 175 deg(2). 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) x 10(-4) d(-1) deg(-2), and a transient surface density of 1.5 x 10(-5) deg(-2), at a 7.9-Jy limiting flux density and similar to 10-min 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 60MHz as a function of observation duration.
techniques: image processing
radio continuum: general