Nova Ejecta Abundances Resulting from Multi-Cycle Evolutionary Calculations

Extract

The theory of nova outbursts invokes accretion of hydrogen-rich material by a white dwarf (WD) in a close binary system, due to Roche lobe overflow of a red dwarf companion, leading to periodic outbursts — powered by thermonuclear runaways — that result in mass ejection. Observed characteristics of novae are reproduced by varying the values of three basic and independent parameters: the accreting white dwarf’s mass, its core temperature, and the mass transfer rate. In a recent study (Prialnik & Kovetz 1995) we have carried out a systematic investigation of nova outbursts on WD progenitors composed of C and O in equal mass fractions, concluding that the entire range of observed nova characteristics could be accounted for. A subset of 34 out of 64 evolutionary sequences (obtained with different parameter combinations) reproduced classical novae, and here we focus on the break-up of the heavy element abundances in the ejecta of these models, in comparison with observations, based on a recent analysis of observed nova abundances by Livio & Truran (1994).