Mass ratios of long-period binary stars resolved in precision astrometry catalogs of two epochs

TL;DR

This paper presents a method to directly estimate mass ratios of long-period binary stars using astrometric data from Hipparcos and Gaia, based on the principle of inertial motion of the system's center of mass, with applications to known binaries.

Contribution

It introduces a novel, assumption-free technique for determining mass ratios from astrometry and extends it to triple systems, including uncertainty estimation methods.

Findings

Applied to HIP 473 AB, deriving a mass ratio of approximately 1.

Method's accuracy depends on data precision, orbital period, and system environment.

Proposed generalization to triple systems enhances applicability.

Abstract

Mass ratios of widely separated, long-period, resolved binary stars can be directly estimated from the available data in major space astrometry catalogs, such as the ESA's Hipparcos and Gaia mission results. The method is based on the universal principle of inertial motion of the system's center of mass in the absence of external forces, and is independent of any assumptions about the physical parameters or stellar models. The application is limited by the precision of input astrometric data, the orbital period and distance to the system, and possible presence of other attractors in the vicinity, such as in triple systems. A generalization of this technique to triples is proposed, as well as approaches to estimation of uncertainties. The known long-period binary HIP 473 AB is discussed as an application example, for which a $m_2/m_1=0.996^{+0.026}_{-0.026}$ is obtained.