Properties of discontinuous and nova-amplified mass transfer in CVs

Abstract

We investigate the effects of discontinuous mass loss in recurrent outburst events on the long-term evolution of cataclysmic variables (CVs). Similarly we consider the effects of frictional angular momentum loss (FAML), i.e. interaction of the expanding nova envelope with the secondary. Numerical calculations of CV evolution over a wide range of parameters demon- strate the equivalence of a discontinuous sequence of nova cycles and the corresponding mean evolution (replacing envelope ejection by a continuous wind), even close to mass transfer instability. A formal stability analysis of discontinuous mass transfer confirms this, independent of details of the FAML model. FAML is a consequential angular momentum loss which amplifies the mass transfer rate driven by systemic angular momentum losses such as magnetic braking. We show that for a given v_exp and white dwarf mass the amplification increases with secondary mass and is significant only close to the largest secondary mass consistent with mass transfer stability. The amplification factor is independent of the envelope mass ejected during the outburst, whereas the mass transfer amplitude induced by individual nova outbursts is proportional to it.Comment: 16 pages, 19 figures; to appear in MNRA