X-ray-to-optical flux ratio vs Gaia (BP–RP) optical color (X-ray main sequence; Rodriguez 2024) for objects in the CSC2–Gaia DR3 catalog. Left panel: Known CVs (red) and stellar objects (STARS, blue) in the CSC2–Gaia DR3 catalog. The dashed black line shows an empirical cut from Rodriguez (2024). The solid red line shows a cut to select a pure sample of CV candidates. Right panel: Objects in the CSC2–Gaia DR3 catalog with the Simbad classifications (which may be imprecise). The colored symbols correspond to the different object types based on the Simbad hierarchical structure (see Table A.1). Objects above the solid red line and variable objects above the dashed black line are classified as new CV candidates (see Tables 1 and B.1). For more details, see Sect. 3.