Astrometric detection of sub-stellar companions with GAIA

Abstract

Observations with the planned astrometry satellite GAIA are modeled in order to determine the detection probabilities for systems consisting of a main-sequence star and a companion of sub-stellar mass. Among the stars within 100 pc from the Sun, most systems having a companion greater than 0.01 solar masses and with periods between 0.25 and 25 yr will be detected. For these systems with periods longer than 10-15 yr, statistical information about orbits is obtained through the curved proper motions. Shorter periods usually result in orbital solutions. For nearly all systems with periods less than five years, accurate orbital elements are obtained from which companion masses can be estimated. For systems having 0.001 solar mass companions, the detection probability exceeds 0.1 in the 1.2-10 yr range. Many of these systems will result in orbital solutions.