Unstable waves in winds of magnetic massive stars

TL;DR

This paper investigates how twisted magnetic fields influence linear waves in massive star winds, potentially explaining high mass-loss rates and wind velocities without conflicting with stellar spin-down constraints.

Contribution

It introduces a model showing magnetic fields can enhance stellar winds and modify wave dynamics, offering explanations for observed wind properties in magnetic massive stars.

Findings

Magnetic fields can drive winds with efficiency >1 without multiple scattering.

Twisted magnetic fields modify radiation-amplified waves, affecting wind acceleration.

The model aligns spin-down times with observed stellar lifetimes.

Abstract

We use a luminous fast magnetic rotator model to analyze the influence of a magnetic field on the linear waves induced in the wind of a massive star by the radiative instability. We show that a twisted magnetic field can drive a strong wind with a wind efficiency $(\dot{M}v_\infty)/(L/c)>1$ even without multiple scattering. The radiation amplified waves in the wind are modified by the twisted magnetic field so that they can enhance the wind and lead to overestimates for $\dot{M}$ and $v_\infty$. Finally we argue that the spin down time might be consistent with the lifetime derived from the mass loss rate within the uncertainties regarding the stellar structure. Therefore our model may help to explain high, observed values for $\dot{M}$ and $v_\infty$ without being ruled out by the spin down problem.