Accretion Processes in CV AM CVn SDSS J090221.35+381941.9

Abstract

SDSS J090221.35+381941.9 is an Cataclysmic Variable AM CVn system that has three most likely evolutionary tracks as defined by the donor type -the hydrogen star channel, the white dwarf channel, and the helium star channel. To break the degeneracy, we numerically model this system three different ways, one for each channel, keeping the mass transfer rate, orbital period, and secondary-to-primary mass ratio constant. Because the white dwarf channel produced a shorter Stage A positive superhump period than in Stage B of the superoutburst, which has never been observed in CV dwarf novae systems, the white dwarf channel has been eliminated as the a likely contender. From a comparison of the system's parameters with the other two evolutionary channels, we find that the helium star channel is most likely for this system and the donor is non-degenerate. As the mass transfer rate is so low, the donor may be starting its evolution into a hybrid white dwarf and migrating from the helium star channel to the white dwarf channel, where it will join its older sibling GP Com.