Stellar atmospheres, atmospheric extension and fundamental parameters: weighing stars using the stellar mass index

TL;DR

This paper introduces a new method to determine the masses of evolved red giant and supergiant stars by analyzing the ratio of different angular diameter measurements, leveraging stellar atmosphere models and observational data.

Contribution

It proposes a novel approach using the stellar mass index derived from interferometric and spectrophotometric observations to measure stellar masses.

Findings

Strong correlation between atmospheric extension and stellar parameters.

Method achieves precise mass measurements for evolved stars.

Potential to improve mass estimates where traditional methods are limited.

Abstract

One of the great challenges in understanding stars is measuring their masses. The best methods for measuring stellar masses include binary interaction, asteroseismology and stellar evolution models, but these methods are not ideal for red giant and supergiant stars. In this work, we propose a novel method for inferring stellar masses of evolved red giant and supergiant stars using interferometric and spectrophotometric observations combined with spherical model stellar atmospheres to measure what we call the stellar mass index, defined as the ratio between the stellar radius and mass. The method is based on the correlation between different measurements of angular diameter, used as a proxy for atmospheric extension, and fundamental stellar parameters. For a given star, spectrophotometry measures the Rosseland angular diameter while interferometric observations generally probe a larger limb-darkened angular diameter. The ratio of these two angular diameters is proportional to the relative extension of the stellar atmosphere, which is strongly correlated to the star's effective temperature, radius and mass. We show that these correlations are strong and can lead to precise measurements of stellar masses.