On the frequency of occurrence of oxygen-neon-magnesium white dwarfs in classical nova systems

The question of the expected frequency of occurrence of oxygen-neon-magnesium (ONeMg) degenerate dwarfs in classical nova systems is examined. Heavy-element abundance enrichments observed in nova ejecta are reviewed, and possible interpretations of their origins are discussed. It is concluded that these abundance enrichments imply the presence of ONeMg white dwarfs, and it is estimated that they might be expected to account for a significant fraction of the observed outbursts. Particular attention is given to providing a realistic estimate of the magnitude of the selection effect which operates to insure the occurrence of a significant population of ONeMg white dwarfs in these systems. The implications of these findings are reviewed, and possible complicating factors are discussed.