The properties and origin of magnetic fields in white dwarfs

TL;DR

This paper reviews the properties, diversity, and potential origins of magnetic fields in white dwarfs, highlighting observational findings and modeling challenges.

Contribution

It provides a comprehensive review of magnetic field characteristics, their variability, and discusses formation scenarios and modeling difficulties in white dwarf atmospheres.

Findings

White dwarfs exhibit magnetic fields from a few kG to 1000 MG.

Magnetic field structures vary from simple dipoles to complex multipoles.

The fraction of magnetic white dwarfs depends on their class.

Abstract

A significant fraction of white dwarfs harbour a magnetic field with strengths ranging from a few kG up to about 1000 MG. The fraction appears to depend on the specific class of white dwarfs being investigated and may hold some clues to the origin of their magnetic field. The number of white dwarfs with variable fields as a function of their rotation phase have revealed a large field structure diversity, from a simple offset dipole to structures with spots or multipoles. A review of the current challenges in modelling white dwarf atmospheres in the presence of a magnetic field is presented, and the proposed scenarios for the formation of magnetic fields in white dwarfs are examined.