ON MASS-TRANSFER RATES IN CLASSICAL NOVA PRECURSORS

A simple model is presented to describe the evolution of cataclysmic variables (CVs). Mass transfer in long-period CVs (P(orb) > 3 hr) is assumed to be due to a magnetic stellar wind and in short-period CVS (P(orb) < 2 hr) to be due to gravitational wave radiation. The critical accreted mass for a classical nova event is adopted to be that for which the thermal structure of the white dwarf is in steady state after many nova events. The frequency with which long-period CVs (accretion rate = 10(-8.2 +/- .6) M. yr-1) experience classical nova outbursts is predicted to be 20-35 times the frequency with which short-period CVs (accretion rate less than 2 x 10(-10) M. yr-1) experience such outbursts, whereas the number of observable CVs with small accretion rates is estimated to be comparable with the number of observable CVs with large accretion rates. Hence, known CVs with small accretion rates are not expected to have experienced a recent nova event and CVs with the highest accretion rates have the greatest chance of being associated with an historical nova. This may help understand why most known precursors and followers of historical novae show high accretion rates.