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) over dot and the central temperature T-c of the white dwarf. According to this relation, for (M) over dot less than 10(-10) M-circle dot yr(-1), T-c is much lower than 10(7) K. Motivated by this study, we follow the thermonuclear runaway on massive white dwarfs (M-WD = 1.25-1.40 M-circle dot) with T-c lower than 10(7) K, accreting matter of solar composition. We demonstrate that in this range of the relevant parameter space (T-c, M-WD, and (M) over dot), the slope of the relation between the peak temperatures achieved during the runaway and T-c becomes much steeper than its value for T-c above 10(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.