X-Ray and Optical Discovery of Rare Cataclysmic Variables

Cataclysmic variables (CVs) are compact object binaries which consist of a white dwarf (WD) accreting from a main-sequence donor star which fills its Roche lobe. CVs are commonly found through their novae and dwarf novae which lead to a transient brightening in time-domain optical surveys. However, rare types of CVs such as magnetic CVs and CVs residing in the “period gap” very rarely undergo dwarf novae or novae, leading them to be elusive in many optical surveys. Magnetic CVs are important astrophysical laboratories since they probe the origin of strong magnetic fields in WDs and inform our understanding of binary star evolution. Magnetic CVs are strong X-ray sources, and previous searches between both X-ray and optical data have led to the discovery of new systems. Period gap CVs are in a low-accretion state, but still remain strong X-ray sources. The eROSITA telescope aboard the Spektr-RG (SRG) mission is conducting an all-sky X-ray survey and has recently released the eROSITA Final Equatorial Depth Survey (eFEDS) catalog. We crossmatch the eFEDS catalog with photometry from the Zwicky Transient Facility (ZTF) and have found two new magnetic CVs and report the X-ray detection of a period gap CV.