We present a search for transient radio sources on time-scales of seconds to hours at 144 MHz using the LOFAR Two-metre Sky Survey (LoTSS). This search is conducted by examining short time-scale images derived from the LoTSS data. To allow imaging of LoTSS on short time-scales, a novel imaging and filtering strategy is introduced. This includes sky model source subtraction, no cleaning or primary beam correction, a simple source finder, fast filtering schemes and source catalogue matching. This new strategy is first tested by injecting simulated transients, with a range of flux densities and durations, into the data. We find the limiting sensitivity to be 113 and 6 mJy for 8 second and 1 hour transients respectively. The new imaging and filtering strategies are applied to 58 fields of the LoTSS survey, corresponding to LoTSS-DR1 (2% of the survey). One transient source is identified in the 8 second and 2 minute snapshot images. The source shows one minute duration flare in the 8 hour observation. Our method puts the most sensitive constraints on/estimates of the transient surface density at low frequencies at time-scales of seconds to hours; <4.0⋅10−4deg−2 at 1 hour at a sensitivity of 6.3 mJy; 5.7⋅10−7deg−2 at 2 minutes at a sensitivity of 30 mJy; and 3.6⋅10−8deg−2 at 8 seconds at a sensitivity of 113 mJy. In the future, we plan to apply the strategies presented in this paper to all LoTSS data.
@article{arxiv.2311.07394,
title = {Transient study using LoTSS -- framework development and preliminary results},
author = {Iris de Ruiter and Zachary S. Meyers and Antonia Rowlinson and Timothy W. Shimwell and David Ruhe and Ralph A. M. J. Wijers},
journal= {arXiv preprint arXiv:2311.07394},
year = {2023}
}