The Effects of Magneto-Convection on Short Period Cataclysmic Variables

TL;DR

This paper models how magneto-convection affects the evolution of short period cataclysmic variables, showing it leads to larger secondary stars, longer orbital periods, and may help resolve the period minimum problem.

Contribution

The study introduces a simple model demonstrating the impact of magneto-convection on cataclysmic variable evolution, highlighting its role in increasing the minimum orbital period.

Findings

Magneto-convection causes larger secondary stars and longer orbital periods.

Including magnetic effects increases the minimum orbital period by 14 minutes.

White dwarf mass has limited impact on the minimum period.

Abstract

Many of the current problems related to the evolution of cataclysmic variables revolve around the magnetic nature of the main sequence secondary. It is known that magnetic fields alter the structure of low mass stars. In particular, they inhibit convection, leading to inflated radii. Here we present a simple model to demonstrate the impact of magneto-convection on the evolution of short period cataclysmic variables. We find that the inclusion of magneto-convection leads to larger secondaries, longer orbital periods and smaller mass-loss rates. When including magnetic effects, the minimum orbital period is increased by 14 minutes, indicating that this could help alleviate the period minimum problem in cataclysmic variable evolution. We also examine the effect of the white dwarf mass on the minimum period. While increasing the white dwarf mass does increase the minimum period, it is not substantial. Therefore it is unlikely that the period minimum problem can be solved with a larger white dwarf mass or with mass growth of white dwarf.