Circumbinary Disks and Cataclysmic Variable Evolution

The influence of a circumbinary (CB) disk on the evolution of cataclysmicvariable (CV) binary systems is investigated. We show that CB mass surfacedensities sufficient to influence the evolution rate are plausibly provided bythe outflows observed in CVs, if the net effect of these winds is to deliver$10^{-4}$--$10^{-3}$ of the mass transfer rate to the CB disk. The torqueexerted by the CB disk provides a positive feedback between mass transfer rateand CB disk mass which can lead to mass transfer rates of $\sim 10^{-8}-10^{-7} \mpy$. This mechanism may be responsible for causing the range ofvariation of mass transfer rates in CV's. In particular, it may explain ratesinferred for the novalike variables and the supersoft X-ray binary systemsobserved near the upper edge of the period gap ($P \sim 3 - 4$ hr), as well asthe spread in mass transfer rates above and below the period gap. Consquencesand the possible observability of such disks are discussed.Comment: submitted to Ap