A giant planet in the triple system HD 132563^⋆,⋆⋆

¹ INAF – Osservatorio Astronomico di Padova, Vicolo dell’ Osservatorio 5, 35122 Padova, Italy
e-mail: silvano.desidera@oapd.inaf.it
² Dipartimento di Astronomia – Universitá di Padova, Vicolo dell’Osservatorio 2, Padova, Italy
³ Fundación Galileo Galilei – INAF, Rambla José Ana Fernandez Pérez, 7 38712 Breña Baja, TF, Spain
⁴ McDonald Observatory, The University of Texas at Austin, Austin, TX 78712, USA
⁵ Observatoire de la Côte d’Azur, Nice, France
⁶ Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto ON, Canada
⁷ INAF – Osservatorio Astrofisico di Catania, via S. Sofia 78, Catania, Italy
⁸ Dipartimento di Fisica – Universitá di Padova, via Marzolo 8, Padova, Italy

Received: 4 May 2011
Accepted: 20 June 2011

Abstract

As part of our radial velocity planet-search survey performed with SARG at TNG, we monitored the components of HD 132563 for ten years. It is a binary system formed by two rather similar solar type stars with a projected separation of 4.1 arcsec, which corresponds to 400 AU at the distance of 96 pc. The two components are moderately metal-poor ([Fe/H] = –0.19), and the age of the system is about 5 Gyr. We detected RV variations of HD 132563B with period of 1544 days and semi-amplitude of 26 m/s. From the star characteristics and line profile measurements, we infer their Keplerian origin. Therefore HD 132563B turns out to host a planet with a projected mass msini = 1.49   M_J at 2.6 AU with a moderately eccentric orbit (e = 0.22). The planet around HD 132563B is one of the few that are known in triple stellar systems, as we found that the primary HD 132563A is itself a spectroscopic binary with a period longer than 15 years and an eccentricity higher than 0.65. The spectroscopic component was not detected in adaptive-optics images taken with the instrument AdOpt mounted at the TNG, since it expected at a projected separation that was smaller than 0.2 arcsec at the time of our observations. A small excess in K band difference between the components with respect to the difference in V band is compatible with a companion of about 0.55   M_⊙. A preliminary statistical analysis of when planets occur in triple systems indicate a similar frequency of planets around the isolated component in a triple system, components of wide binaries and single stars. There is no significant iron abundance difference between the components. The lack of stars in binary systems and open clusters showing strong enhancements of iron abundance, which are comparable to the typical metallicity difference between stars with and without giant planets, agrees with the idea that accretion of planetary material producing iron abundance anomalies over 0.1 dex is rare.