Convective overshoot mixing in Nova outbursts - The dependence on the composition of the underlying white dwarf

TL;DR

This study uses 2D simulations to explore how the composition of the white dwarf's underlying layer affects convective mixing during nova outbursts, revealing significant enrichment across various compositions.

Contribution

First 2D analysis of convective overshoot in novae across diverse white dwarf compositions, expanding understanding beyond solar and C-O cases.

Findings

Significant enrichment of underlying materials in nova ejecta across all compositions.

Convective dredge-up leads to helium enrichment in recurrent novae.

Results align with observational data.

Abstract

We present here, for the first time, a 2D study of the overshoot convective mechanism in nova outbursts for a wide range of possible compositions of the layer underlying the accreted envelope. Previous surveys studied this mechanism only for solar composition matter accreted on top of carbon oxygen (C-O) white dwarfs. Since, during the runaway, mixing with carbon enhances the hydrogen burning rates dramatically, one should question whether significant enrichment of the ejecta is possible also for other underlying compositions (He, O, Ne, Mg), predicted by stellar evolution models. We simulated several non-carbon cases and found significant amounts of those underlying materials in the ejected hydrogen layer. Despite large differences in rates, time scales and energetics between the cases, our results show that the convective dredge up mechanism predicts significant enrichment in all our non-carbon cases, including helium enrichment in recurrent novae. The results are consistent with observations.