Binary component masses from Gaia

Using a likelihood approach, we sample the posterior probability distribution over the stellar parameters, marginalizing over system age and metallicity to get the individual masses. We apply this to 20000 systems with a main sequence primary within 300pc of the Sun using data from the Gaia data release 3 non-single star catalogue. Primary masses can be determined with a precision (one-sigma posterior width) of 10-20% in 90% of cases.

Secondary masses, which extend down to planetary-mass objects, are less precise, although half are more than 25% precise. Interestingly, adding either infrared photometry or spectroscopic orbits from Gaia does not change the mass estimates much (less than 4% and 1% respectively). Interstellar extinction likewise has little impact for this sample.

This work shows that reasonably precise masses can be obtained for stars and substellar objects using just the Gaia astrometry and photometry without need for extensive follow-up.