Discovery of a Meter-Wavelength Radio Transient in the SWIRE Deep Field: 1046+59

TL;DR

This study used archival low-frequency radio observations to discover a new transient event in the SWIRE Deep Field, revealing a rare day-scale radio transient with no known counterpart and estimating its occurrence rate.

Contribution

It reports the first detection of a day-scale radio transient at 325 MHz in the SWIRE Deep Field, demonstrating the effectiveness of archival data for transient searches.

Findings

Detected one day-scale transient event with no known counterpart.

Estimated transient rate of 1±1 per 6.5 deg² per 72 hours.

Established a surface density of 0.12 deg⁻² for sources above 2.1 mJy.

Abstract

We report the results of a low frequency radio variability and slow transient search using archival observations from the Very Long Array. We selected six 325 MHz radio observations from the spring of 2006, each centered on the Spitzer-Space-Telescope Wide-area Infrared Extragalactic Survey (SWIRE) Deep Field: 1046+59. Observations were spaced between 1 day to 3 months, with a typical single-epoch peak flux sensitivity below 0.2 \mjb near the field pointing center. We describe the observation parameters, data post-processing, and search methodology used to identify variable and transient emission. Our search revealed multiple variable sources and the presence of one, day-scale transient event with no apparent astronomical counterpart. This detection implies a transient rate of 1$\pm$1 event per 6.5 $\deg^2$ per 72 observing hours in the direction of 1046+59 and an isotropic transient surface density $\Sigma = 0.12 \deg^{-2}$ at 95% confidence for sources with average peak flux density higher than 2.1 mJy over 12 hr.