Angular Diameters and Effective Temperatures of Twenty-five K Giant Stars from the CHARA Array

TL;DR

This study provides precise angular diameters and effective temperatures for 25 K giant stars using interferometry, improving accuracy over photometric methods and highlighting discrepancies with spectroscopic estimates.

Contribution

First interferometric measurements of angular diameters and temperatures for 25 K giant stars, offering more accurate stellar parameters than previous photometric estimates.

Findings

Angular diameters match photometric estimates within errors.

Effective temperatures differ from spectroscopic values.

Measurements have lower uncertainties than prior methods.

Abstract

Using Georgia State University's CHARA Array interferometer, we measured angular diameters for 25 giant stars, six of which host exoplanets. The combination of these measurements and Hipparcos parallaxes produce physical linear radii for the sample. Except for two outliers, our values match angular diameters and physical radii estimated using photometric methods to within the associated errors with the advantage that our uncertainties are significantly lower. We also calculated the effective temperatures for the stars using the newly-measured diameters. Our values do not match those derived from spectroscopic observations as well, perhaps due to the inherent properties of the methods used or because of a missing source of extinction in the stellar models that would affect the spectroscopic temperatures.