The white dwarf mass distribution in classical nova systems

Using a detailed theoretical model for the distribution of white dwarf masses in newly formed cataclysmic binaries produced by close binary evolution, we derive model distributions for the nova outbursts which subsequently occur among these systems, taking due account of selection effects imposed by the dependences of envelope ignition mass, companion mass, and outburst luminosity on the masses of white dwarfs in nova systems. Those selection effects all favor the most massive white dwarfs and produce a prominent maximum in outburst frequency as a function of mass at the limiting mass for white dwarfs, with a much weaker maximum at 0.71 M_⊙ (the peak of the underlying white dwarf mass distribution). In accord with earlier estimates by Truran and Livio, we find that a substantial fraction (25%-57%) of observed nova outbursts should occur on O-Ne-Mg white dwarfs, the balance nearly all occurring on C-O white dwarfs with a negligible contribution from He white dwarfs. The mean white dwarf mass (by nova frequency) is estimated at 1.04-1.24 M_⊙, slightly higher than the mean of 0.90 M_⊙ estimated observationally. We note some evidence of a bimodal character to the empirical nova white dwarf mass distribution as expected from our models. The total nova frequency which we derive for the solar neighborhood is approximately one order of magnitude smaller than observational estimates, but it is not clear even so that this discrepancy is significant in view of model uncertainties.