Evolution of a long-period Cataclysmic Variable from the viewpoint of the donor star: the case of SDSS J085210.48+783246.6

Cataclysmic variables were long considered to be close binaries consisting of a white dwarf and a Roche-lobe-filling, near-zero-age main-sequence (ZAMS) red or brown dwarf. Recent massive surveys have uncovered an increasing number of binaries with similar spectral characteristics but harboring secondary stars that have undergone nuclear evolution and partial envelope stripping, many with orbital periods far exceeding the normal upper limits for ordinary CVs. We present a detailed study of a newly discovered CV with a 17.109 h period and determine its basic stellar parameters. We also discuss the evolutionary paths leading to the formation of these extremely long-period cataclysmic variables. We consider the implications of the new evolutionary hypothesis on their further evolution into double-degenerate binaries.