Methodology for obtaining the relative orbit and individual masses of Gaia astrometric binaries

Abstract

Context. The recent Gaia Data Release 3 has revealed a catalogue of more than eight hundred thousand binary systems. The release provides orbital solutions for half of the systems, with the majority of them being unresolved astrometric binaries. However, some astrophysical parameters are still unknown for most of them, such as the spectral type and the mass of each companion, since they can only be derived from the relative orbit and spectroscopic data. Aims. The purpose of this work is to develop a methodology that would allow us to obtain those fundamental stellar parameters, along with those related to the geometry and the ephemeris of the system, to find out whether it can be optically resolved. Methods. To obtain precise values for each component, we proposed an analytic algorithm to estimate the only two possible relative orbits and pairs of masses of main sequence (MS) astrometric binaries using all the available astrometric, photometric, and spectro-scopic data from Gaia DR3. In some cases, it is possible to select the solution that is more aligned with the rest of the data. Results. We deduced two possible values for the individual absolute magnitudes, masses, and effective temperatures for each binary, as well as the size of the telescope necessary to resolve their components. We present the workflow of our algorithm applied to the Ephemeris, Stellar Masses, and relative ORbits from GAia (ESMORGA) catalogue, along with the individual masses, absolute magnitudes, and effective temperatures derived for 49 530 binaries.