Double degenerate mergers as progenitors of high-field magnetic white dwarfs

TL;DR

This paper proposes that mergers of two degenerate stellar cores can produce high-field magnetic white dwarfs through a convective corona, with simulations matching observed populations.

Contribution

It demonstrates that stellar mergers can generate strong magnetic fields in white dwarfs via a convective corona, providing a plausible formation mechanism.

Findings

Convective corona in merger remnants produces strong, long-lasting magnetic fields.

Monte Carlo simulations align the predicted and observed numbers of high-field magnetic white dwarfs.

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.