# The metallicity dependence of WR winds

## TL;DR

This paper reviews spectral analyses of Wolf-Rayet stars across different metallicities, deriving empirical relations for how their mass-loss rates depend on metallicity and iron abundance, which impacts stellar evolution models.

## Contribution

It provides the first comprehensive empirical relations linking WR star mass-loss rates to metallicity and iron content based on spectral analysis across diverse environments.

## Key findings

- Mass-loss rates increase with metallicity.
- Derived empirical relations for WN star mass-loss dependence.
- Implications for stellar evolution in low-metallicity environments.

## Abstract

Wolf-Rayet (WR) stars are the most advanced stage in the evolution of the most massive stars. The strong feedback provided by these objects and their subsequent supernova (SN) explosions are decisive for a variety of astrophysical topics such as the cosmic matter cycle. Consequently, understanding the properties of WR stars and their evolution is indispensable. A crucial but still not well known quantity determining the evolution of WR stars is their mass-loss rate. Since the mass loss is predicted to increase with metallicity, the feedback provided by these objects and their spectral appearance are expected to be a function of the metal content of their host galaxy. This has severe implications for the role of massive stars in general and the exploration of low metallicity environments in particular. Hitherto, the metallicity dependence of WR star winds was not well studied. In this contribution, we review the results from our comprehensive spectral analyses of WR stars in environments of different metallicities, ranging from slightly super-solar to SMC-like metallicities. Based on these studies, we derived empirical relations for the dependence of the WN mass-loss rates on the metallicity and iron abundance, respectively.