The Origin of Magnetism in White Dwarfs

TL;DR

This paper explores the origins of magnetism in white dwarfs, examining the relationship between magnetic fields, binarity, and stellar evolution processes, especially during common envelope phases.

Contribution

It investigates the hypothesis that white dwarf magnetic fields are generated through dynamo mechanisms during common envelope evolution, contrasting with other formation theories.

Findings

Magnetic white dwarfs are rare in wide binaries with non-degenerate companions.

The dynamo mechanism during common envelope evolution is a plausible origin for white dwarf magnetism.

The presence of magnetic fields may be linked to binary interaction history.

Abstract

The absence of magnetic white dwarfs with a non-degenerate low-mass stellar companion in a wide binary is still very intriguing and at odds with the hypothesis that magnetic white dwarfs are the progenies of the magnetically peculiar Ap/Bp stars. On the other hand, we cannot resort to a process that impedes the generation of a strong magnetic field in the main or pre-main sequence progenitors of white dwarfs if they are in a multiple stellar system, because such a process would also prevent the formation of magnetic cataclysmic variables consisting of a magnetic white dwarf accreting mass from a low-mass companion. This is the reason why it has been proposed that fields in white dwarfs may be linked to their binarity and are generated through a dynamo mechanism during common envelope evolution.