Accurate Low-Mass Stellar Models of KOI-126

TL;DR

This paper presents stellar models for the KOI-126 system that accurately match observed radii, highlighting the importance of the equation of state and revealing dispersion in the mass-radius relation for low-mass stars.

Contribution

The study provides stellar models that align with observations for KOI-126, emphasizing the role of the equation of state and discussing the variability in low-mass star properties.

Findings

Models match observed stellar radii in KOI-126

Dispersion observed in mass-radius relation for low-mass stars

Predicted apsidal motion constants with high observational accuracy

Abstract

The recent discovery of an eclipsing hierarchical triple system with two low-mass stars in a close orbit (KOI-126) by Carter et al. (2011) appeared to reinforce the evidence that theoretical stellar evolution models are not able to reproduce the observational mass-radius relation for low-mass stars. We present a set of stellar models for the three stars in the KOI-126 system that show excellent agreement with the observed radii. This agreement appears to be due to the equation of state implemented by our code. A significant dispersion in the observed mass-radius relation for fully convective stars is demonstrated; indicative of the influence of physics currently not incorporated in standard stellar evolution models. We also predict apsidal motion constants for the two M-dwarf companions. These values should be observationally determined to within 1% by the end of the Kepler mission.