CARBON-NITROGEN-OXYGEN “BREAKOUT” AND NUCLEOSYNTHESIS IN CLASSICAL NOVAE

Abstract

For very slow white dwarf accretors in CV's Townsley and Bildsten (2004)\nfound a relation between the accretion rate and the central temperature of the\nwhite dwarf Tc. According to this relation for accretion rates less than 10^-10\nsolar masses per year Tc is much lower than 10^7 K.\n Motivated by this study we follow the thermonuclear runaway on massive white\ndwarfs (M_WD=1.25 - 1.40 solar masses) with Tc lower than 10^7 K, accreting\nmatter of solar composition. We demonstrate that in that range of the relevant\nparameter space (Tc,M_WD and accretion rate) the slope of the relation between\nthe peak temperatures achieved during the runaway and Tc becomes much steeper\nthan its value for Tc above 10^7 K. The peak temperatures we derive can lead to\nnuclear breakout from the conventional "hot carbon-nitrogen-oxygen" cycle. When\nbreakout conditions are achieved the heavy element abundances can show a much\nwider variety than what is possible with the common enrichment mechanisms.\n