7.3 Alternative astrometric orbit processing
Author(s): Alessandro Sozzetti, Berry Holl, Johannes Sahlmann
This section describes the solutions produced by the development unit responsible for fitting Keplerian parameters to astrometric epoch data of low signal-to-noise ratio (SNR) orbits, like the ones corresponding to planetary-mass or brown-dwarf companions as well as near-equal mass binaries: for spatially-unresolved binaries, the astrometry reflects the motion of the combined photocentre, which for near-equal magnitude binaries is much smaller than the actual astrometric motion of each individual component around their barycentre. This pipeline channel processed 2 457 530 sources that were not sufficiently well modelled in terms of acceleration or binary orbital fits of the non-single stars pipeline (Section 7.2) and ended up with a (non-published) so-called ‘stochastic’ solution. For 629 sources in this stochastic solution sample an orbital fit was produced and is published in the nss_two_body_orbit table with nss_solution_type, OrbitalAlternative (619) and OrbitalAlternativeValidated (10).
For Gaia DR3 an independent, targeted search for significant astrometric orbital signals was performed for a set of almost 20 000 sources, which included host stars with known exoplanet, brown-dwarf, and stellar companions. The composition of the targeted search sample is described in Holl et al. (2023b). The 533 sources identified in this search are found in the nss_two_body_orbit table with nss_solution_type OrbitalTargetedSearch (345) and OrbitalTargetedSearchValidated (188).