The Incidence of Dwarf Novae in Large Area Transient Searches

Understanding and quantifying the contribution of known classes of transientand variable sources is an important lesson to be learned from the manifold ofpre-cursors programs of the near-future large synoptic sky survey programs likeSkyMapper, Pan-STARRS and LSST. With this goal in mind, we undertookphotometric and spectroscopic follow-up observations of three recently reportedunidentified transients. For two sources, WFI J132813.7-214237 and WFIJ161953.3+031909, we show that unfortunate coincidences lead to their previousdesignation as transients. While the former is now interpreted as the spatialcoincidence of a solar system object with faint background star, the latter ismerely a cataclysmic variable unfortunately caught in and out of eclipse. Thethird candidate, ROTSE3 J160213.1-021311.7 is identified as an SU UMa-typedwarf novae with quiescent brightness of R~22.7 and an outburst amplitude ofabout 5 mag. The fourth event, SDSS-SN15207, similarly shows evidence for adwarf nova origin. Our main conclusion is that cataclysmic variables in theirvarious avata rs will contribute moderately to the population of transientobjects.Comment: ApJ in pres