Multiplicity of stars with planets in the solar neighbourhood

¹ Departamento de Física de la Tierra y Astrofísica & IPARCOS-UCM (Instituto de Física de Partículas y del Cosmos de la UCM), Facultad de Ciencias Físicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
² UNIE Universidad, Departamento de Ciencia y Tecnología, c/ Arapiles 14, 28015 Madrid, Spain
³ Centro de Astrobiología (CSIC-INTA), European Space Astronomy Centre, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain

Received: 20 March 2024
Accepted: 26 July 2024

Abstract

Aims. We intended to quantify the impact of stellar multiplicity on the presence and properties of exoplanets.

Methods. We investigated all exoplanet host stars at less than 100 pc using the latest astrometric data from Gaia DR3 and advanced statistical methodologies. We complemented our search for common proper motion and parallax companions with data from the Washington Double Star catalogue and the literature. After excluding a number of systems based on radial velocity data, and membership in clusters and open associations, or with resolved ultracool companions, we kept 215 exoplanet host stars in 212 multiple-star systems.

Results. We found 17 new companions in the systems of 15 known exoplanet host stars, and we measured precise angular and projected physical separations and position angles for 236 pairs of stars, compiled key parameters for 276 planets in multiple systems, and established a comparison sample comprising 687 single stars with exoplanets. With all of this, we statistically analysed a series of hypotheses regarding planets in multiple stellar systems. Although they are only statistically significant at a 2σ level, our analysis pointed to several interesting results on the comparison in the mean number of planets in multiple versus single stellar systems and the tendency of high-mass planets to be located in closer orbits in multiple systems. We confirm that planets in multiple systems tend to have orbits with larger eccentricities than those in single systems. In particular, we found a significant (>4σ) preference for planets to exhibit high orbital eccentricities at small ratios between star-star projected physical separations and star-planet semi-major axes.