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 and the central temperature T _c of the white dwarf. According to this relation, for less than 10^-10 _M yr^-1, T _c is much lower than 10⁷ K. Motivated by this study, we follow the thermonuclear runaway on massive white dwarfs (M _WD = 1.25-1.40 _M) with T _c lower than 10⁷ K, accreting matter of solar composition. We demonstrate that in this range of the relevant parameter space (T _c, M _WD, and ), 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 10⁷ 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.