On the origin of macroturbulence in hot stars

TL;DR

This paper proposes that macroturbulence in hot stars' spectral lines is caused by collective non-radial gravity-mode pulsations, offering a physical explanation for the observed line broadening.

Contribution

It introduces a pulsational velocity broadening model to explain macroturbulence, challenging the traditional Gaussian assumption and improving stellar rotational velocity estimates.

Findings

Macroturbulence can be explained by non-radial gravity-mode oscillations.

Incorrect assumptions about macroturbulence lead to underestimated rotational velocities.

The proposed model aligns better with observed spectral line profiles.

Abstract

Since the use of high-resolution high signal-to-noise spectroscopy in the study of massive stars, it became clear that an ad-hoc velocity field at the stellar surface, termed macroturbulence, is needed to bring the observed shape of spectral lines into agreement with observations. We seek a physical explanation of this unknown broadening mechanism. We interprete the missing line broadening in terms of collective pulsational velocity broadening due to non-radial gravity-mode oscillations. We also point out that the rotational velocity can be seriously underestimated whenever the line profiles are fitted assuming a Gaussian macroturbulent velocity rather than an appropriate pulsational velocity expression.