Weighing the Darkness II: Astrometric Measurement of Partial Orbits with Gaia

Understand

Over the course of several years, stars trace helical trajectories as they traverse across the sky due to the combined effects of proper motion and parallax.

• It is well known that the gravitational pull of an unseen companion can cause deviations to these tracks.
• Several studies have pointed out that the astrometric mission Gaia will be able to identify a slew of new exoplanets, stellar binaries, and compact object companions with orbital periods as short as tens of days to as long as Gaia's lifetime.
• Here, we use mock astrometric observations to demonstrate that Gaia can identify and characterize black hole companions to luminous stars with orbital periods longer than Gaia's lifetime.