White Dwarf/M Dwarf Binaries as Single Degenerate Progenitors of Type Ia Supernovae

TL;DR

This paper explores the potential of white dwarf/M dwarf binary systems as progenitors of Type Ia supernovae, emphasizing magnetic interactions, accretion processes, and the possibility of white dwarf mass growth beyond the nova limit.

Contribution

It introduces the idea that magnetic fields and flaring M dwarfs can facilitate mass transfer and growth of white dwarfs to the Chandrasekhar limit, offering a new perspective on supernova progenitors.

Findings

Magnetic locking induces polar accretion, enhancing mass transfer.

Magnetic fields and flaring activity can enable white dwarfs to reach Chandrasekhar mass.

Magnetic inhibition of mixing may help white dwarfs surpass the nova limit.

Abstract

Limits on the companions of white dwarfs in the single degenerate scenario for the origin of Type Ia supernovae (SNIa) have gotten increasingly tight. The only type of non-degenerate stars that survive the limits on the companions of SNIa in SNR 0509-67.5 and SN1572 are M dwarfs. M dwarfs have special properties that have not been considered in most work on the progenitors of SNIa: they have small but finite magnetic fields, and they flare frequently. These properties are explored in the context of SNIa progenitors. White dwarf/M dwarf pairs may be sufficiently plentiful to provide an adequate rate of explosions. Even modest magnetic fields on the white dwarf and M dwarf will yield adequate torques to lock the two stars together, resulting in a slowly rotating white dwarf, with the magnetic poles pointing at one another in the orbital plane. The mass loss will be channeled by a "magnetic bottle" connecting the two stars, landing on a concentrated polar area on the white dwarf. This enhances the effective rate of accretion compared to spherical accretion. Luminosity from accretion and hydrogen burning on the surface of the white dwarf may induce self-excited mass transfer. The combined effects of self-excited mass loss, polar accretion, and magnetic inhibition of mixing of accretion layers give possible means to beat the "nova limit" and grow the white dwarf to the Chandrasekhar mass even at rather moderate mass accretion rates.