Detached Red Giant Eclipsing Binary Twins: Rosetta Stones to the Galactic Bulge

TL;DR

This paper identifies red giant eclipsing binary systems in the Galactic Bulge that can provide independent constraints on stellar populations and Galactic evolution through spectroscopic measurements.

Contribution

It presents a method to use detached red giant eclipsing binaries as tools for constraining the age, metallicity, and helium content of the Galactic Bulge, offering a new approach to Galactic archaeology.

Findings

34 probable systems identified in OGLE-II catalog

At least 200 such systems expected in OGLE-III

Spectroscopic data can break degeneracies in Bulge stellar population models

Abstract

We identify 34 highly-probable detached, red giant eclipsing binary pairs among 315 candidates in Devor's catalog of $\sim$10,000 OGLE-II eclipsing binaries. We estimate that there should be at least 200 such systems in OGLE-III. We show that spectroscopic measurements of the metallicities and radial-velocity-derived masses of these systems would independently constrain both the age-metallicity and helium-metallicity relations of the Galactic Bulge, potentially breaking the age-helium degeneracy that currently limits our ability to characterize the Bulge stellar population. Mass and metallicity measurements alone would be sufficient to immediately validate or falsify recent claims about the age and helium abundance of the Bulge. A spectroscopic survey of these systems would constrain models of Milky Way assembly, as well as provide significant auxiliary science on research questions such as mass loss on the red giant branch. We discuss the theoretical uncertainties in stellar evolution models that would need to be accounted for to maximize the scientific yield.