Cataclysmic Variables (hereafter, CVs) are binary stars made of a white dwarf which is accreting mass from a less evolved companion which is loosing mass through Roche-lobe overflow. Given the parameters of the system (mass ratio, magnetic field of either component, orbital inclination and mass accretion), CVs can show a variety of different appearances.
CVs are known to host classical nova explosions (whenever the material accreted on the white dwarf reaches the critical pressure to start thermonuclear reactions), which, among other things, are considered responsible for the production of Li in the Universe. Novae (and CVs, in general) are widely considered among possible progenitors of type Ia supernovae (SNe Ia). While the study of the explosion properties of SNe Ia has been widely conducted over the last decades (even bringing to a Nobel Prize "for the discovery of the accelerating expansion of the Universe through observations of distant supernovae"), the knowledge of the progenitors of these explosions is still very limited.
So far, CVs have been mostly discovered as by-products of projects aimed at (very) different scientific topics. For example, many broad band photometric surveys have identified CVs while looking for quasars (see Gaensicke 2005 for more details). Similarly, the Catalina Sky Surveys (CSS) have identified CVs through their variability while aiming (mostly) at asteroids and transients.
The filters of J-PLUS are ideally suited for the identification of CVs, hence reducing the probability to mix these objects with quasars. The spectral energy distributions of CVs can be blue and/or red and often show emission lines. Using these characteristics, they are normally comparatively easy to distinguish from "normal" stars. The combination of broad and narrow band filters will increase significantly our ability to detect CVs unambiguously.
The characteristics of J-PLUS, its depth, sky area and unique filter set, will provide for the first time a magnitude-limited unbiased sample of CVs, which will allow us to study the evolutionary properties of these objects, their role as nova and supernova progenitors as well as study mass-accretion physics.