A study of the electrostatic properties of the interiors of low-mass stars: Possible implications for the observed rotational properties

TL;DR

This paper investigates electrostatic effects in low-mass star interiors and their correlation with stellar rotation, using models to understand how plasma physics influences observable stellar properties and magnetic activity.

Contribution

It introduces a global plasma parameter to compare electrostatic interactions across models and correlates these effects with stellar rotation and magnetic activity trends.

Findings

Electrostatic effects correlate with stellar rotation rates.

Variations in electrostatic interactions relate to age and metallicity.

Insights may explain weakened magnetic braking in stars.

Abstract

In the partially ionized material of stellar interiors, the strongest forces acting on electrons and ions are the Coulomb interactions between charges. The dynamics of the plasma as a whole depend on the magnitudes of the average electrostatic interactions and the average kinetic energies of the particles that constitute the stellar material. An important question is how these interactions of real gases are related to the observable stellar properties. Specifically, the relationships between rotation, magnetic activity, and the thermodynamic properties of stellar interiors are still not well understood. In this study, we investigate the electrostatic effects within the interiors of low-mass main sequence (MS) stars. Specifically, we introduce a global quantity, a global plasma parameter, which allows us to compare the importance of electrostatic interactions across a range of low-mass theoretical models ($0.7 - 1.4 \, M_\odot$) with varying ages and metallicities. We then correlate the electrostatic properties of the theoretical models with the observable rotational trends on the MS. We use the open-source 1D stellar evolution code MESA to compute a grid of main-sequence stellar models. Our models span the $\log g - T_{\text{eff}}$ space of a set of 66 Kepler main-sequence stars. We identify a correlation between the prominence of electrostatic effects in stellar interiors and stellar rotation rates. The variations in the magnitude of electrostatic interactions with age and metallicity further suggest that understanding the underlying physics of the collective effects of plasma can clarify key observational trends related to the rotation of low-mass stars on the MS. These results may also advance our understanding of the physics behind the observed weakened magnetic braking in stars.