The radius and mass of the subgiant star bet Hyi from interferometry and asteroseismology

TL;DR

This study combines interferometry and asteroseismology to precisely measure the radius, temperature, and mass of the subgiant star beta Hyi, providing tighter constraints on stellar models.

Contribution

It presents the first direct interferometric measurement of beta Hyi's angular diameter and combines it with asteroseismology to accurately determine its fundamental parameters.

Findings

Radius of 1.814 solar radii with 0.9% precision

Mass of 1.07 solar masses with 2.8% precision

Effective temperature of 5872 K with 0.7% precision

Abstract

We have used the Sydney University Stellar Interferometer (SUSI) to measure the angular diameter of beta Hydri. This star is a nearby G2 subgiant whose mean density was recently measured with high precision using asteroseismology. We determine the radius and effective temperature of the star to be 1.814+/-0.017 R_sun (0.9%) and 5872+/-44 K (0.7%) respectively. By combining this value with the mean density, as estimated from asteroseismology, we make a direct estimate of the stellar mass. We find a value of 1.07+/-0.03 M_sun (2.8%), which agrees with published estimates based on fitting in the H-R diagram, but has much higher precision. These results place valuable constraints on theoretical models of beta Hyi and its oscillation frequencies.