Fundamental Properties of Cool Stars with Interferometry

TL;DR

This study measures the radii and temperatures of nearby low-mass stars using interferometry, revealing that convection significantly influences stellar radii and highlighting discrepancies with theoretical models that impact exoplanet research.

Contribution

The paper provides new empirical measurements of stellar radii and temperatures for cool stars, and offers insights into the causes of radius discrepancies with theoretical predictions.

Findings

Convection influences the radii of late-type stars.

Discrepancies exist between observed and theoretical stellar radii.

Empirical relations for stellar temperature and radius are established.

Abstract

We present measurements of fundamental astrophysical properties of nearby, low-mass, K- and M-dwarfs from our DISCOS survey (DIameterS of COol Stars). The principal goal of our study is the determination of linear radii and effective temperatures for these stars. We calculate their radii from angular diameter measurements using the CHARA Array and Hipparcos distances. Combined with bolometric flux measurements based on literature photometry, we use our angular diameter results to calculate their effective surface temperatures. We present preliminary results established on an assortment of empirical relations to the stellar effective temperature and radius that are based upon these measurements. We elaborate on the discrepancy seen between theoretical and observed stellar radii, previously claimed to be related to stellar activity and/or metallicity. Our preliminary conclusion, however, is that convection plays a larger role in the determination of radii of these late-type stars. Understanding the source of the radius disagreement is likely to impact other areas of study for low-mass stars, such as the detection and characterization of extrasolar planets in the habitable zones.