Cool Subdwarf Investigations III: Dynamical Masses of Low Metallicity Subdwarfs

TL;DR

This paper measures the dynamical masses of low-metallicity subdwarfs using Hubble data, compares them to models, and discusses the scarcity of such measurements and the need for further research.

Contribution

It provides new dynamical mass measurements for subdwarfs and compares them to theoretical models, enhancing the empirical mass-luminosity relation for low metallicity stars.

Findings

Dynamical masses for G 006-026 B and C obtained.

Most stars align with low metallicity model predictions.

Highlights the need for more precise measurements and data.

Abstract

We report dynamical mass measurements for the components of the previously known double-lined spectroscopic subdwarfs G 006-026 B and C using the Fine Guidance Sensors (FGS) on the Hubble Space Telescope. To build the empirical mass-luminosity relation for low metallicity subdwarfs, we collect four other subdwarf systems with dynamical masses that we compare to theoretical models for various metallicities on the mass-luminosity relation. For most stars, they fall in the regions where the models predict to be low metallicity. This effort highlights the scarcity of dynamical masses for subdwarfs and that much work remains to be done to improve the mass errors and metallicity measurements of low mass subdwarfs in our Galaxy.