Spindown of massive rotating stars

TL;DR

This paper investigates how magnetic dynamos influence the spin-down of rapidly rotating massive stars at low metallicity, revealing that such stars can lose angular momentum quickly, limiting their high rotation phase.

Contribution

It introduces a model for magnetic dynamo-driven spin-down in massive stars, quantifying the time-scale and showing rapid rotation is short-lived.

Findings

Spin-down time-scale can be a small fraction of the main-sequence lifetime.

Higher surface rotation speeds lead to faster spin-down.

Rapid rotators may only display high velocities briefly during their evolution.

Abstract

Models of rapidly rotating massive stars at low metallicities show significantly different evolution and higher metal yields compared to non-rotating stars. We estimate the spin-down time-scale of rapid rotating non-convective stars supporting an alpha-Omega dynamo. The magnetic dynamo gives rise to mass loss in a magnetically controlled stellar wind and hence stellar spin down owing to loss of angular momentum. The dynamo is maintained by strong horizontal rotation-driven turbulence which dominates over the Parker instability. We calculate the spin-down time-scale and find that it could be relatively short, a small fraction of the main-sequence lifetime. The spin-down time-scale decreases dramatically for higher surface rotations suggesting that rapid rotators may only exhibit such high surface velocities for a short time, only a small fraction of their main-sequence lifetime.