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

Abstract

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 10-10M 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. © 2009. The American Astronomical Society. All rights reserved..