The influence of metallicity on stellar differential rotation and magnetic activity

TL;DR

This study reveals how increased stellar metallicity influences magnetic activity and differential rotation, demonstrating that higher metallicity can lead to stronger brightness variability in Sun-like stars.

Contribution

First observational evidence showing metallicity's effect on stellar dynamo and activity cycles in Sun-like stars, linking metallicity to enhanced variability.

Findings

HD 173701 has a 7.4-year activity cycle similar to the Sun.

Higher metallicity correlates with stronger brightness variability.

Metallicity influences the depth of the convection zone and facular contrast.

Abstract

Observations of Sun-like stars over the last half-century have improved our understanding of how magnetic dynamos, like that responsible for the 11-year solar cycle, change with rotation, mass and age. Here we show for the first time how metallicity can affect a stellar dynamo. Using the most complete set of observations of a stellar cycle ever obtained for a Sun-like star, we show how the solar analog HD 173701 exhibits solar-like differential rotation and a 7.4-year activity cycle. While the duration of the cycle is comparable to that generated by the solar dynamo, the amplitude of the brightness variability is substantially stronger. The only significant difference between HD 173701 and the Sun is its metallicity, which is twice the solar value. Therefore, this provides a unique opportunity to study the effect of the higher metallicity on the dynamo acting in this star and to obtain a comprehensive understanding of the physical mechanisms responsible for the observed photometric variability. The observations can be explained by the higher metallicity of the star, which is predicted to foster a deeper outer convection zone and a higher facular contrast, resulting in stronger variability.