Wide Binaries in Tycho-{\it Gaia}: Search Method and the Distribution of Orbital Separations

Understand

We mine the Tycho-{\it Gaia} astrometric solution (TGAS) catalog for wide stellar binaries by matching positions, proper motions, and astrometric parallaxes.

• We separate genuine binaries from unassociated stellar pairs through a Bayesian formulation that includes correlated uncertainties in the proper motions and parallaxes.
• Rather than relying on assumptions about the structure of the Galaxy, we calculate Bayesian priors and likelihoods based on the nature of Keplerian orbits and the TGAS catalog itself.
• We calibrate our method using radial velocity measurements and obtain 6196 high-confidence candidate wide binaries with projected separations $s\lesssim1$ pc.