Intermediate-Mass Stars Become Magnetic White Dwarfs

TL;DR

This study discovers magnetic white dwarfs in young star clusters, suggesting that intermediate-mass stars can directly evolve into magnetic white dwarfs, challenging previous merger-based theories.

Contribution

It provides evidence that intermediate-mass progenitors can produce magnetic white dwarfs through single-star evolution, not just mergers.

Findings

Discovery of two massive magnetic white dwarfs in young clusters.

Progenitor masses above 5 solar masses for these white dwarfs.

High incidence of magnetic white dwarfs from intermediate-mass stars.

Abstract

When a star exhausts its nuclear fuel, it either explodes as a supernova or more quiescently becomes a white dwarf, an object about half the mass of our Sun with a radius of about that of the Earth. About one fifth of white dwarfs exhibit the presence of magnetic fields, whose origin has long been debated as either the product of previous stages of evolution or of binary interactions. We here report the discovery of two massive and magnetic white dwarf members of young star clusters in the Gaia DR2 database, while a third massive and magnetic cluster white dwarf was already reported in a previous paper. These stars are most likely the product of single-star evolution and therefore challenge the merger scenario as the only way to produce magnetic white dwarfs. The progenitor masses of these stars are all above 5 solar masses, and there are only two other cluster white dwarfs whose distances have been unambiguously measured with Gaia and whose progenitors' masses fall in this range. This high incidence of magnetic white dwarfs indicates that intermediate-mass progenitors are more likely to produce magnetic remnants and that a fraction of magnetic white dwarfs forms from intermediate-mass stars.