Fundamental Properties of Late-Type Stars in Eclipsing Binaries

TL;DR

This study revisits the properties of late-type stars in eclipsing binaries, highlighting discrepancies with models likely due to magnetic activity, and emphasizes the need for improved models and more data.

Contribution

Updated list of 32 eclipsing binary systems with precise measurements, and analysis of discrepancies between observations and stellar models considering magnetic activity.

Findings

Discrepancies of about 7% in radius and -4% in temperature compared to models.

Magnetic activity likely causes observed size and temperature differences.

Discrepancies may be larger below the full convection boundary.

Abstract

Evidence from the analysis of eclipsing binary systems revealed that late-type stars are larger and cooler than predicted by models, and that this is probably caused by stellar magnetic activity. In this work, we revisit this problem taking into account the advancements in the last decade. We provide and updated a list of 32 eclipsing binary or multiple systems, including at least one star with a mass $\lesssim 0.7$ M$_{\odot}$ and with mass and radius measured to an accuracy better than 3%. The~comparison with stellar structure and evolution theoretical models reveals an overall discrepancy of about 7% and -4% for the radius and effective temperature, respectively, and that it may be larger than previously found below the full convection boundary. Furthermore, the hypothesis of stellar activity is reinforced by the comparison of different systems with similar components. Further eclipsing binaries with accurately determined masses and radii, and with estimated activity levels, as well as the implementation of magnetic activity in theoretical models will help to improve our knowledge of low-mass stars, which are prime targets for exoplanet surveys.