Stellar Diameters and Temperatures I. Main Sequence A, F, & G Stars

TL;DR

This study measures the angular diameters and effective temperatures of 44 main sequence A, F, and G stars using the CHARA Array, compares these with models and previous estimates, and refines temperature calibration methods.

Contribution

First direct interferometric measurements of stellar diameters and temperatures for a significant sample of main sequence stars, improving calibration accuracy and model comparisons.

Findings

Models overestimate effective temperatures by 1.5-4%.

Interferometric temperatures agree well with eclipsing binary data.

Calibration of stellar temperatures with ~1% error is achievable.

Abstract

We have executed a survey of nearby, main sequence A, F, and G-type stars with the CHARA Array, successfully measuring the angular diameters of fortyfour stars with an average precision of ~ 1.5%. We present new measures of the bolometric flux, which in turn leads to an empirical determination of the effective temperature for the stars observed. In addition, these CHARA-determined temperatures, radii, and luminosities are fit to Yonsei-Yale model isochrones to constrain the masses and ages of the stars. These results are compared to indirect estimates of these quantities obtained by collecting photometry of the stars and applying them to model atmospheres and evolutionary isochrones. We find that for most cases, the models overestimate the effective temperature by ~ 1.5-4%, when compared to our directly measured values. The overestimated temperatures and underestimated radii in these works appear to cause an additional offset in the star's surface gravity measurements, which consequently yield higher masses and younger ages, in particular for stars with masses greater than ~1.3 Msun. Additionally, we compare our measurements to a large sample of eclipsing binary stars, and excellent agreement is seen within both data sets. Finally, we present temperature relations with respect to (B-V) and (V-K) color as well as spectral type showing that calibration of effective temperatures with errors ~ 1% is now possible from interferometric angular diameters of stars.