Discovery of a stellar companion to HD 131399A ⋆
1 Institut de Planétologie et d’Astrophysique de Grenoble, UMR 5274 CNRS, Université Grenoble-Alpes, 38000 Grenoble, France
2 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
3 ESO, Alonso de Cordova 3107, Casilla 19001, Santiago 19, Chile
Received: 12 April 2017
Accepted: 10 May 2017
Context. The giant exoplanets imaged on wide orbits (≥10 au) around young stars challenge the classical theories of planet formation. The presence of perturbing bodies could have played a role in the dynamical evolution of the planets once formed.
Aims. We aim to search for close companions to HD 131399, a star around which a giant planet has been discovered, at a projected separation of about 80 au. The star also appears to be a member of a wide (320 au) binary system.
Methods. We recorded HARPS high resolution spectra in January 2017.
Results. We find that HD 131399A is probably seen close to pole-on. We discover a low mass star companion that orbits with a period of about 10 days on a misaligned orbit. Even though the companion does not have an impact on the current dynamical evolution of the planet, it could have played a role in its setting and in clearing the circumstellar disk from which the planet may originate.
Key words: techniques: radial velocities / planetary systems / binaries: close / stars: individual: HD 131399
© ESO, 2017