On the origin of high-field magnetic white dwarfs

TL;DR

This paper proposes that the magnetic fields in high-field magnetic white dwarfs originate from the convective, differentially rotating corona formed during stellar mergers, supported by simulations matching observed populations.

Contribution

It introduces a new model linking stellar mergers to magnetic field generation in white dwarfs, supported by Monte Carlo simulations.

Findings

The merger remnant corona can generate long-lasting magnetic fields of observed strength.

The predicted number of magnetic white dwarfs aligns with observed counts in the solar neighborhood.

The proposed mechanism explains the origin of high magnetic fields in white dwarfs.

Abstract

High-field magnetic white dwarfs have been long suspected to be the result of stellar mergers. However, the nature of the coalescing stars and the precise mechanism that produces the magnetic field are still unknown. Here we show that the hot, convective, differentially rotating corona present in the outer layers of the remnant of the merger of two degenerate cores is able to produce magnetic fields of the required strength that do not decay for long timescales. We also show, using an state-of-the-art Monte Carlo simulator, that the expected number of high-field magnetic white dwarfs produced in this way is consistent with that found in the solar neighborhood.