Magnetic braking with MESA evolutionary models in the single star and LMXB regimes

TL;DR

This study evaluates different magnetic braking models in stellar evolution, finding that a model with a rapid transition and magnetic field topology effects best explains observed binary and star rotation data, but not the stalled spin-down in older low-mass stars.

Contribution

It identifies a magnetic braking prescription that aligns with observed binary periods and star rotation rates, emphasizing the role of magnetic field topology effects.

Findings

Data favors a braking model with rapid transition and saturation.

The preferred model reproduces ultra-compact X-ray binaries.

None of the models explain stalled spin-down in older low-mass stars.

Abstract

Magnetic braking has a prominent role in driving the evolution of close low mass binary systems and heavily influences the rotation rates of low mass F- and later type stars with convective envelopes. Several possible prescriptions that describe magnetic braking in the context of 1D stellar evolution models currently exist. We test four magnetic braking prescriptions against both low mass X-ray binary orbital periods from the Milky Way and single star rotation periods observed in open clusters. We find that data favors a magnetic braking prescription that follows a rapid transition from fast to slow rotation rates, exhibits saturated (inefficient) magnetic braking below a critical Rossby number, and that is sufficiently strong to reproduce ultra compact X-ray binary systems. Of the four prescriptions tested, these conditions are satisfied by a braking prescription that incorporates the effect of high order magnetic field topology on angular momentum loss. None of the braking prescriptions tested are able to replicate the stalled spin down observed in open cluster stars aged 700 - 1000 Myr or so, with masses $\lesssim$ 0.8 $\rm M_{\odot}$.