Astrometric mass ratios of 248 long-period binary stars resolved in Hipparcos and Gaia EDR3

TL;DR

This study derives mass ratios for 248 long-period binary stars by comparing astrometric data from Hipparcos and Gaia EDR3 over 24.75 years, providing a new catalog without relying on astrophysical assumptions.

Contribution

It introduces a method to compute binary star mass ratios using only astrometric data from two space missions, avoiding traditional assumptions.

Findings

Catalog of 248 binary systems with mass ratios

Identification of systems with unusual properties

Validation of astrometric method for long-period binaries

Abstract

Using the absolute astrometric positions and proper motions for common stars in the Hipparcos and Gaia catalogs separated by 24.75 years in the mean epoch, we compute mass ratios for long-period, resolved binary systems without any astrophysical assumptions or dependencies except the presence of inner binary subsystems that may perturb the observed mean proper motions. The mean epoch positions of binary companions from the Hipparcos Double and Multiple System Annex (DMSA) are used as the first epoch. The mean positions and proper motions of carefully cross-matched counterparts in Gaia EDR3 comprise the second epoch data. Selecting only results with sufficiently high signal-to-noise ratio and discarding numerous optical pairs, we construct a catalog of 248 binary systems, which is published online. Several cases with unusual properties or results are also discussed.