Magnetic white dwarfs with debris disks

TL;DR

This paper proposes a model where magnetic white dwarfs with debris disks experience spin-down due to magnetosphere-disk interactions, explaining observed slow rotation periods and supporting a merger origin.

Contribution

It introduces a new model of magnetosphere-disk interaction that accounts for the slow rotation of magnetic white dwarfs, addressing previous discrepancies in merger scenarios.

Findings

Model predicts significant spin down of magnetic white dwarfs.

Reproduces the observed rotation period of REJ 0317-853.

Supports merger origin hypothesis for magnetic white dwarfs.

Abstract

It has long been accepted that a possible mechanism for explaining the existence of magnetic white dwarfs is the merger of a binary white dwarf system, as there are viable mechanisms for producing sustainable magnetism within the merger product. However, the lack of rapid rotators in the magnetic white dwarf population has been always considered a problematic issue of this scenario. In order to explain this discrepancy we build a model in which the interaction between the magnetosphere of the star and the disk induces angular momentum transfer. Our model predicts that the magnetospheric interaction of magnetic white dwarfs with their disks results in a significant spin down, and we show that the observed rotation period of REJ 0317-853, which is suggested to be a product of a double degenerate merger, can be reproduced.