Nova-induced mass transfer variations

Abstract

We investigate variations of the mass transfer rate in cataclysmic variables (CVs) that are induced by nova outbursts. The ejection of nova shells leads to a spread of transfer rates in systems with similar orbital period. The effect is maximal if the specific angular momentum in the shell is the same as the specific orbital angular momentum of the white dwarf. We show analytically that in this case the nova-induced widening of the mass transfer rate distribution can be significant if the system, in the absence of nova outbursts, is close to mass transfer instability (i.e., within a factor of ~1.5 of the critical mass ratio). Hence the effect is negligible below the period gap and for systems with high-mass white dwarfs. At orbital periods between about 3 and 6 hrs the width of the mass transfer rate distribution exceeds an order of magnitude if the mass accreted on the white dwarf prior to the runaway is larger than a few 10^{-4} M_sun. At a given orbital period in this range, systems with the highest transfer rate should on average have the largest ratio of donor to white dwarf mass. We show results of population synthesis models which confirm and augment the analytic results.