White dwarf spins from low mass stellar evolution models

TL;DR

This study compares stellar evolution models with and without magnetic fields to observational data, revealing that magnetic torques are essential to explain the slow rotation rates of white dwarfs.

Contribution

It introduces detailed stellar evolution models including rotation and magnetic fields, providing new insights into white dwarf spin predictions and their alignment with observations.

Findings

Magnetic models predict white dwarf spins consistent with observations

Non-magnetic models overestimate white dwarf rotational velocities

Magnetic torques are likely necessary to explain slow stellar remnant rotation

Abstract

The prediction of the spins of the compact remnants is a fundamental goal of the theory of stellar evolution. Here, we confront the predictions for white dwarf spins from evolutionary models including rotation with observational constraints. We perform stellar evolution calculations for stars in the mass range 1... 3$\mso$, including the physics of rotation, from the zero age main sequence into the TP-AGB stage. We calculate two sets of model sequences, with and without inclusion of magnetic fields. From the final computed models of each sequence, we deduce the angular momenta and rotational velocities of the emerging white dwarfs. While models including magnetic torques predict white dwarf rotational velocities between 2 and 10 km s$^{-1}$, those from the non-magnetic sequences are found to be one to two orders of magnitude larger, well above empirical upper limits. We find the situation analogous to that in the neutron star progenitor mass range, and conclude that magnetic torques may be required in order to understand the slow rotation of compact stellar remnants in general.