Evolution of the number of accreting white dwarfs with shell nuclear burning and of occurrence rate of SN Ia

TL;DR

This study models the evolution of accreting white dwarfs with shell nuclear burning and examines their connection to Type Ia supernovae, finding mergers are the dominant scenario in both burst and continuous star formation systems.

Contribution

It provides a detailed analysis of white dwarf populations and their potential to produce Type Ia supernovae under different star formation histories.

Findings

Most supersoft X-ray sources are not SN Ia precursors after 10 Gyr.

White dwarf mergers dominate the SN Ia scenario in both systems.

Accreting CO-dwarfs in symbiotic binaries do not reach SN Ia mass thresholds.

Abstract

We analyze temporal evolution of the number of accreting white dwarfs with shell hydrogen burning in semidetached and detached binaries. We consider a stellar system in which star formation lasts for 10 Gyr with a constant rate, as well as a system in which the same amount of stars is formed in a single burst lasting for 1 Gyr. Evolution of the number of white dwarfs is confronted to the evolution of occurrence rate of events that usually are identified with SN Ia or accretion-induced collapses, i.e. with accumulation of Chandrasekhar mass by a white dwarf or a merger of a pair of CO white dwarfs with total mass not lower than the Chandrasekhar one. In the systems with a burst of star formation, at $t=$10 Gyr observed supersoft X-ray sources, most probably, are not precursors of SN Ia. The same is true for an overwhelming majority of the sources in the systems with constant star formation rate. In the systems of both kinds mergers of white dwarfs is the dominant SN Ia scenario. In symbiotic binaries, accreting CO-dwarfs do not accumulate enough mass for SN Ia explosion, while ONeMg-dwarfs finish their evolution by an accretion-induced collapse with formation of a neutron star.