Modelling Mixing in Novae outbursts: A New Approach for 1-Dimensional Simulations

Abstract Nova-hosting white dwarfs (WDs) have long been considered as the likely progenitors of type-Ia supernovae through the single-degenerate channel of evolution. In this scenario, the WD grows in mass with every nova outburst until it reaches the Chandrasekhar mass limit. Classical Nova eruptions have historically been disregarded as potential candidates for this channel of evolution as they are assumed to either decrease in mass with every outburst or increase in mass too slowly. However, these assumptions are based on single-nova outburst simulations or incorrect nova-modelling methods. The material ejected into the interstellar medium from classical nova events are observed to be enriched in CNO elements and sometimes other intermediate-mass elements such as Ne, Na, Mg and Al depending on the composition of the underlying WD (CO- or ONe-rich). This suggests that the solar-like material transferred from the WDs companion star becomes mixed with the underlying WD. In 1-D nova simulations, this mixing was conventionally modelled by accreting material already pre-enriched with WD matter atop a WD which subsequently lead to unrealistic nova outbursts. To improve upon this, a new method of convectively mixing WD and envelope material has been developed for the stellar evolution code MESA based on the recent results multi-D nova mixing studies. This method will be used to investigate the possibility of a WD growing to the Chandrasekhar mass limit through many classical nova eruptions in a more realistic way to previous studies.