The Incidence of Dwarf Novae in Large Area Transient Searches

Abstract

Understanding and quantifying the contribution of known classes of transient and variable sources is an important lesson to be learned from the manifold of pre-cursors programs of the near-future large synoptic sky survey programs like SkyMapper, Pan-STARRS and LSST. With this goal in mind, we undertook photometric and spectroscopic follow-up observations of three recently reported unidentified transients. For two sources, WFI J132813.7-214237 and WFI J161953.3+031909, we show that unfortunate coincidences lead to their previous designation as transients. While the former is now interpreted as the spatial coincidence of a solar system object with faint background star, the latter is merely a cataclysmic variable unfortunately caught in and out of eclipse. The third candidate, ROTSE3 J160213.1-021311.7 is identified as an SU UMa-type dwarf novae with quiescent brightness of R~22.7 and an outburst amplitude of about 5 mag. The fourth event, SDSS-SN15207, similarly shows evidence for a dwarf nova origin. Our main conclusion is that cataclysmic variables in their various avata rs will contribute moderately to the population of transient objects.