The CORALIE survey for southern extrasolar planets

XIX. Brown dwarfs and stellar companions unveiled by radial velocity and astrometry^★,★★

¹ Department of Astronomy, University of Geneva, Chemin Pegasi 51, 1290 Versoix, Switzerland
e-mail: domenico.barbato@unige.ch
² INAF – Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese, Italy
³ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁴ European Southern Observatory, Casilla, 19001, Santiago, Chile
⁵ ETH Zurich, Department of Physics, Wolfgang-Pauli-Strasse 2, 8093 Zurich, Switzerland
⁶ Astrophysics Group, Cavendish Laboratory, JJ Thomson Avenue, CB3 0HE Cambridge, UK
⁷ Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal
⁸ Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal

Received: 9 January 2023
Accepted: 29 March 2023

Abstract

Context. A historical search for exoplanets among a sample of 1647 nearby southern main sequence stars with the CORALIE spectrograph at La Silla Observatory has been underway since 1998, with a backup subprogram dedicated to the monitoring of binary stars.

Aims. We reviewed 25 years of CORALIE measurements and search for Doppler signals consistent with stellar or brown dwarf companions to produce an updated catalog of both known and previously unpublished binary stars in the planet-search sample. We assessed the binarity fraction of the stellar population and survey the prospects for more precise searches for planets in the binary sample.

Methods. We performed a new analysis on the CORALIE planet-search sample’s radial velocity measurements, searching for stellar companions and obtaining orbital solutions for both known and new binary systems. We performed simultaneous radial velocity and proper motion anomaly fits on the subset of these systems for which HIPPARCOS and Gaia astrometry measurements are available, obtaining accurate estimates of true mass for the companions.

Results. We found 218 stars in the CORALIE sample to have at least one stellar companion, 130 of which are not yet published in the literature and for which we present orbital solutions. The use of the proper motion anomaly allowed us to derive true masses for the stellar companions in 132 systems, which we additionally used to estimate stability regions for possible planetary companions on circumprimary or circumbinary orbits. Finally, we produced detection-limit maps for each star in the sample and obtained occurrence rates of 0.43_−0.11^+0.23% and 12.69_−0.77^+0.87% for brown dwarf and stellar companions, respectively, in the CORALIE sample.