PiGSS. III. ELAIS-N1, Coma & Lockman fields

We compare the catalogs generated from the combined images to those from individual epochs, and from monthly averages, as well as to legacy surveys. We undertake a search for transients, with particular emphasis on excluding false positive sources. We find no confirmed transients, defined here as sources that can be shown to have varied by at least a factor of 10.

However, we find one source that brightened in a single-epoch image to at least six times the upper limit from the corresponding deep image. We also find a source associated with a z=0.6 quasar which appears to have brightened by a factor ~3 in one of our deep images, when compared to catalogs from legacy surveys. We place new upper limits on the number of transients brighter than 10mJy: fewer than 0.08 transients deg^-2^ with characteristic timescales of months to years; fewer than 0.02deg^-2^ with timescales of months; and fewer than 0.009deg^-2^ with timescales of days.

We also plot upper limits as a function of flux density for transients on the same timescales.