CNO "Breakout" and Nucleosynthesis in Classical Novae
Abstract
For very slow white dwarf accretors in CV's Townsley and Bildsten (2004) found a relation between the accretion rate and the central temperature of the white dwarf Tc. According to this relation for accretion rates less than 10-10 solar masses per year Tc is much lower than 107 K. Motivated by this study we follow the thermonuclear runaway on massive white dwarfs (MWD=1.25 - 1.40 solar masses) with Tc lower than 107 K, accreting matter of solar composition. We demonstrate that in that range of the relevant parameter space (Tc,MWD and accretion rate) the slope of the relation between the peak temperatures achieved during the runaway and Tc becomes much steeper than its value for Tc 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.