CNO Abundances and Hydrodynamic Models of the Nova Outburst

Abstract

We have used a fully implicit, Lagrangian, hydrodynamic computer code incorporating a nuclear reaction network to follow thermonuclear runaways in the hydrogen-rich envelopes of white dwarfs in order to produce a nova outburst Because of the short timescales and the high nuclear burning rates produced in our models (T > 3 X 108 K and 8 > 1018 ergs ) the nuclear reactions are far out of equilibrium and the p+-unstable nuclei become the most abundant nuclei in the envelope except for hydrogen and helium. Our models have ejected 1.7 X t0- e with kinetic energies of 8 X 10 ergs a value that agrees quite closely with the observed values for novae. We have varied the initial abundance of the CNO nuclei and find that the actual ejection of material and production of an outburst requires these nuclei to be strongly enhanced and that observed features of the outburst depend on the degree of CNO enhancement. The final isotopic abundances in the ejected material do not correspond to equilibrium CNO burning and are a strong test of our model for the outburst.