Searching for substellar companion candidates with Gaia. II. A catalog of 9,698 planet candidate solar-type hosts

TL;DR

This study builds a GaiaPMEX-based catalog of 9,698 planet-candidate host stars by exploiting RUWE and PMa signals in Gaia DR3 to infer a companion mass and sma, focusing on planetary-mass companions ($M_c<13.5\,M_{\rm J}$) within 1–3 au. The authors define a ruwe-based astrometric signature and its significance, derive mass–sma relations with two period regimes, and apply a six-step selection process to construct the catalog, achieving a low false-positive rate around $2.7\sigma$ (p<0.00694). Cross-matches with Gaia NSS/H Holl et al. classifications and NEA exoplanet catalogs show substantial agreement and reveal that several known planets and brown dwarfs are captured, while many candidates remain subject to degeneracy and require follow-up. The Hipparcos-focused subset identifies four new planetary candidates and several BD/star companions, illustrating GaiaPMEX's strength in identifying potentially novel planetary systems in the solar neighborhood. Overall, the work demonstrates Gaia's potential to expand exoplanet demographics, provides a vetted input catalog for future follow-up, and outlines paths to extend the method to M-dwarfs and fainter targets.

Abstract

In a previous paper, we introduced a new tool called GaiaPMEX. It characterizes the mass and semi-major axis relative to the central star (sma) of a possible companion around any source observed with Gaia. It uses the value of RUWE, or, with both Gaia and Hipparcos, the value of proper motion anomaly (PMa), alone or combined with the RUWE. Our goal is to exploit the large volume of sources in Gaia's DR3 and find new exoplanet candidates. We wish to create a new input catalog of planet-candidate hosting systems to the disposal of future follow-up projects. Beyond G=14, this catalog would prepare the arrival of powerful instruments on the ELTs, that could include RV follow-up of faint stars and direct imaging of planets around main sequence Gyr-old stars. We used the mass-sma degenerate set of solutions obtained by GaiaPMEX from any value of RUWE to select a sample of bright (G<16) Gaia sources whose companions could be planetary, with a mass <13.5 MJup. It led us to identify a sample of 9,698 planet candidate hosting sources, whose companion may have a mass <13.5 MJup in the range of 1-3-au sma. We identified 19 systems that are also reported in the Nasa exoplanet archive. We detected 8 substellar companions with a 1-3-au sma, initially discovered and characterised with RV and astrometry. Moreover, we found 6 transiting-planet systems and 2 wide-orbit systems for whom we predict the existence of supplementary companions. Focusing on the subsample of sources observed with Hipparcos, combining RUWE and PMa, we confirmed the identification of 4 new planetary candidate systems HD 187129, HD 81697, CD-42 883, and HD 105330. Given the degeneracy of mass-sma, many of the candidates in this 9,698 sources catalog might have a larger mass, in the brown-dwarf and stellar domain, if their sma departs from the 1-3-au range. The vetting of this large catalog will be the subject of future studies.

Figures (12)

• Figure 1: pmex confidence map of the mass and sma of a companion around GJ 832 constrained by the ruwe. The darkest area delineated with a black solid line spans the 68.3% confidence region. The gradually lighter purple areas delineated with black dashed and dotted lines, respectively, span the 95.4% and 99.7% confidence regions. This example is described in detail in Paper I. The thick dark lines show the mass--sma relationship of Eq. \ref{['eq:mass_sma_AEN']}. The yellow circle shows the $M\sin i$ and sma of the known Jupiter-like planet in this system Philipot2023b.
• Figure 2: Selection steps used to build the sample of candidate systems with exoplanet companions, where six selection criteria ($C_0$ to $C_5$) are applied iteratively.
• Figure 3: Hertzsprung-Russell diagrams throughout the sequence of the selection steps presented in Fig. \ref{['fig:steps']}. The different steps are shown as follows: the sources at S1 whose absolute magnitude $M_G$ is not corrected for extinction and $Bp-Rp$ is not corrected for reddening are shown in black; the sources with an existing mass in the CU8 catalog and whose $G$ and $Bp-Rp$ are corrected for extinction and reddening are shown in green, and those that are moreover nongiant and without photometric mass are shown in red; and the final 9,698 planet-candidate hosts are shown in blue.
• Figure 4: Fraction of FPs among selected planet candidates at different significance criteria ($N$--$\sigma$) in the 5p (blue) and 6p (orange) datasets. The black solid line shows the 10% level.
• Figure 5: Distribution of the locations in the plane of the sky, in galactic coordinates, of planet-candidate hosts from the 5p (blue) and 6p (orange) datasets, compared to all the sources in the input sample at step 3 (black).