The <i>Gaia</i> spectroscopic catalogue of exoplanets and host stars

Context. Complete, accurate, and precise catalogues of exoplanet host star (EHS) properties are essential to deriving high-quality exoplanet parameters. These datasets can then be used to study individual planets, planet populations, and planet formation within their Galactic context. Aims. This paper is aimed at homogeneously parameterising EHS and their exoplanets, selected from the Encyclopedia of Exo-planetary Systems and the NASA Exoplanets Archive, using Gaia astrometric, photometric, and GSP-Spec spectroscopic data, complemented by some ground-based spectroscopic survey information. Methods. From the atmospheric parameters of 2573 EHS, we computed their luminosity, radius, and mass, with no prior assumption from stellar evolution models. Their Galactic positions, kinematic and orbital properties were also derived. We then re-scaled the mass and radius of 3556 exoplanets, fully consistently with the stellar data (when available). Results. The Gaia spectroscopic stellar effective temperatures, luminosities, and radii are in rather good agreement with literature values but are more precise. In particular, stellar radii are derived with typically less than 3% uncertainty (instead of ~ 8% in the literature); this reduces the uncertainty on the planetary radii significantly and allows for a finer analysis of the decrease in the number of planets around 1.8 R ⊕ (evaporation valley). Larger differences, however, were found for the masses that are more difficult to estimate by any methods. We note that the EHS population is rather diverse in terms of the chemical and Galactic properties, although they are all found in the Solar vicinity, close to the Local spiral arm. Most EHS belong to the thin disc, but some older thick disc and halo members have also been identified. For the less massive planets (log( M p / M Jup ) ≲ -0.6), the average planet radius increases with the metallicity of the host star. For giant planets, a dichotomy between dense and inflated planets is found. Denser planets ( R p ≲ 1.1 R Jup ) tend to be more massive as the metallicity of the host star increases, while inflated planets are more massive for less metallic hosts. If confirmed, this bimodality implies that the diversity of giant exoplanets depends on their Galactic birth locus, with dense giant planets being more numerous than inflated ones when [M/H] is higher than ~1.5 times Solar, as in the central Milky Way regions. Conclusions. The Gaia spectroscopic catalogue of exoplanets and their host stars is large, homogeneous, and precise. Thus, it would be a useful added-value for planetary studies. Since it is based on literature data, it can also easily be updated thanks to future Gaia data releases and other space- and ground-based surveys.