Radial Velocity Orbital Solutions for Candidate Black Hole and Neutron Star Binary Systems in the Gaia Data Release 3 Catalog

TL;DR

This paper analyzes Gaia DR3 binary systems to identify potential black hole or neutron star companions, providing orbital solutions and classifications, and highlighting the need for more conservative selection criteria to improve reliability.

Contribution

It offers spectroscopic followup and orbital solutions for Gaia DR3 binaries, revealing inaccuracies in previous Gaia orbits and proposing improved selection methods for dark companion candidates.

Findings

Gaia orbits are incorrect for stars with candidate dark companions above 2 Msun.

No new confirmed black hole or neutron star companions were found.

One system likely contains a neutron star or ultramassive white dwarf with a minimum companion mass of 1.16 Msun.

Abstract

We present spectroscopic followup observations of binary systems from the Gaia Data Release 3 (DR3) binary catalog that were selected to have large enough mass functions for their companions to be black holes or neutron stars. The selection includes 20 stars that are astrometric and/or spectroscopic binaries, as well as 11 stars with large accelerations both in the plane of the sky and along the line of sight but no DR3 orbital solution. We provide classifications for this entire sample, including radial velocity orbital solutions for 11 binaries. Apart from the previously published binaries Gaia BH1, Gaia BH2, and Gaia NS1, we show that the Gaia orbits are incorrect for all of the stars with candidate dark companions above 2 Msun. We suggest more conservative cuts on the significance and goodness of fit parameters that may be useful for identifying reliable orbital solutions in the tail of the binary star distribution. Although we find no new confirmed black hole or neutron star companions, one accelerating system has a minimum companion mass of 1.16 +/- 0.01 Msun that is likely to be a neutron star or an ultramassive white dwarf. The acceleration catalogs may therefore provide a largely unexplored source of additional wide binaries containing compact objects.