Orbits and Masses for 156 Companions from Combined Astrometry and Radial Velocities, and A Validation of Gaia Non-Single Star Solutions

TL;DR

This study combines multiple astrometric and radial velocity data sources to derive orbits and masses for 156 stellar companions, validating Gaia DR3 solutions and revealing the brown dwarf desert up to 10 AU.

Contribution

It provides the first comprehensive mass and orbit measurements for a diverse set of companions and validates Gaia non-single-star solutions against independent data.

Findings

Detection of the brown dwarf desert beyond 10 AU.

Qualitative agreement between predicted and Gaia DR3 accelerations.

Identification of limitations in Gaia orbital solutions for long-period systems.

Abstract

We combine absolute astrometry from Hipparcos and Gaia with archival radial velocities from the Keck/HIRES and ESO/HARPS spectrographs, as well as relative astrometry (when available), to derive masses and orbits for 156 companions around main-sequence stars, including 111 stellar companions, 12 brown dwarfs, and 33 planets. Although this sample is not compiled for occurrence-rate statistics due to systematic biases in non-uniform target selection and varied observing strategies, we nonetheless clearly detect the Brown Dwarf desert in the distribution of companion masses (as well as in mass ratio), out to separations of more than 10 AU. This work also enables a validation of Gaia DR3 non-single-star solutions by predicting Gaia's measured Right Ascension and Declination acceleration terms. For stars with Gaia astrometric acceleration solutions, we find qualitative agreement with Gaia DR3 results. Our predicted accelerations agree with the Gaia DR3 values overall, showing a median offset of 1.85 sigma, with a tail extending to about 10 sigma. These residuals suggest modestly underestimated uncertainties, broadly consistent with previous results for parallaxes and proper motions. Three of our systems have full Gaia orbital fits; however, their true orbital periods are long and all three Gaia solutions are spurious. Gaia DR4 will provide individual astrometric measurements and enable more detailed and extensive investigations of accelerating and orbital fits.