Astrometric mass measurement of compact companions in binary systems with <i>Gaia</i>

For binary systems with an unseen primary and a luminous secondary, the astrometric wobble of secondary could be used to study primary. With Gaia, it is possible measure mass black hole or neutron star companion (hereafter BH/NS-LC). Our aim provide method for predicting Gaia's ability in measuring BH/NS-LCs. We also tried estimate number solvable BH/NS-LCs using Gaia. realistic Markov chain Monte Carlo simulation mock Gaia observations obtain relation between uncertainty measurement observable variables orbit. Furthermore, we MOBSE code evolve Galactic BH/NS-LC sample combined Milky Way model. applied this derived good parameters. first time, show quantitive influence period P, inclination i, eccentricity e, ecliptic latitude $\beta$ measurement. results suggest that $48^{+7}_{-7}$ BH-LCs $102^{+11}_{10}$ NS-LCs are during 5 yr mission. give distribution distance apparent magnitude This would increased by additional spectroscopic data prolonged The future simulations observed prediction not only influenced process generating sample, but affected our relation. In particular, relations parameters such as $[P, \beta]$ very useful correct selection effect statistic