Carbon-nitrogen-oxygen "breakout" and nucleosynthesis in classical novae

For very slow white dwarf accretors in cataclysmic variables, Townsley & Bildsten found a relation between the accretion rate M and the central temperature T{sub c} of the white dwarf. According to this relation, for M less than 10{sup -10} M {circle_dot} yr{sup -1}, T{sub c} is much lower than 10{sup 7} K. Motivated by this study, we follow the thermonuclear runaway on massive white dwarfs (M{sub WD} = 1.25-1.40 M {circle_dot}) with T{sub c} lower than 10{sup 7} K, accreting matter of solar composition. We demonstrate that in this range of the relevant parameter space (T{sub c}, M{sub WD}, and M), the slope of the relation between the peak temperatures achieved during the runaway and T{sub c} becomes much steeper than its value for T{sub c} above 10{sup 7} K. The peak temperatures we derive can lead to nuclear breakout from the conventional ''hot carbon-nitrogen-oxygen'' cycle. When breakout conditions are achieved the heavy-element abundances can show a much wider variety than what is possible with the common enrichment mechanisms.