A Sample of Neutron Star and Black Hole Binaries Detected through Gaia DR3 Astrometry

Understand

With its exquisite astrometric precision, the latest Gaia data release includes $\sim$$10^5$ astrometric binaries, each of which have measured orbital periods, eccentricities, and the Thiele-Innes orbital parameters.

• Using these and an estimate of the luminous stars' masses, we derive the companion stars' masses, from which we identify a sample of 24 binaries in long period orbits ($P_{\rm orb}\sim{\rm yrs}$) with a high probability of hosting a massive ($>$1.4 $M_{\odot}$), dark companion: a neutron star (NS) or black hole (BH).
• The luminous stars in these binaries tend to be F-, G-, and K-dwarfs with the notable exception of one hot subdwarf.
• Follow-up spectroscopy of eight of these stars shows no evidence for contamination by white dwarfs or other luminous stars.