The Cause of the Nova Outburst

Abstract

We have evolved a large number of models of thermonuclear runaways in the hydrogen-rich envelopes of 1.00 M⊙ carbon-oxygen white dwarfs. Models characterized by enhanced CNO abundances satisfy the observations of the common nova outburst. They eject from 1027 to 1029 g moving with velocities of 200–2400 km s−1: kinetic energies of 1044 to 1045 erg. The theoretical light curves are similar to the observed light curves of common novae during the early stages of the outburst. As a consequence of our studies, we can present an explanation for the continuous ejection of mass which is observed for long times after the initial outburst and for the relationship between maximum magnitude and the decline to minimum. We are also now able to present an explanation for the constant luminosity phase of the outburst and the oval shapes of the ejected nebulae.We have extended our earlier work to models with extreme enhancements of 12C and to models which include the infalling material in the evolution. The extreme 12C studies result in outbursts which reach near supernova proportions while the accretion models result in light curves which resemble observed light curves quite closely. Finally, the accretion studies also demonstrate the need for enhanced abundances.