The VLT/NaCo large program to probe the occurrence of exoplanets and brown dwarfs in wide orbits

I. Sample definition and characterization ^{⋆,⋆⋆,⋆⋆⋆}

¹ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
e-mail: silvano.desidera@oapd.inaf.it
² INAF – Osservatorio Astronomico di Napoli, Salita Moiariello 16, 80131 Napoli, Italy
³ INAF – Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy
⁴ Department of Physics & Astronomy, College of Charleston, 58 Coming St. Charleston, SC 29424, USA
⁵ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁶ Geneva Observatory, University of Geneva, Chemin des Maillettes 51, 1290 Versoix, Switzerland
⁷ Institut de Planétologie et d’Astrophysique de Grenoble, UJF, CNRS, 414 rue de la piscine, 38400 Saint-Martin d’ Hères, France
⁸ Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
⁹ Department of Physics and Astronomy, Faculty of Science, Macquarie University, Sydney NSW, 2109, Australia
¹⁰ Instituto de Astrofisica de Canarias, C/ Via Lactea, s/n, 38205, La Laguna, Tenerife, Spain
¹¹ Universitá di Catania, Dipartimento di Fisica e Astronomia, via S. Sofia 78, 95123 Catania, Italy
¹² European Southern Observatory, Casilla 19001 Santiago 19, Chile
¹³ Institute for Astronomy, ETH Zurich, Wolfgang-Pauli Strasse 27, 8093 Zurich, Switzerland

Received: 2 December 2013
Accepted: 22 April 2014

Abstract

Context. Young, close stars are ideal targets for searching planets using the direct imaging technique. The determination of stellar parameters is crucial for the interpretation of imaging survey results, particularly since the luminosity of substellar objects has a strong dependence on system age.

Aims. We have conducted a large program with NaCo at the VLT to search for planets and brown dwarfs in wide orbits around 86 stars. A large fraction of the targets observed with NaCo were poorly investigated in the literature. We performed a study to characterize the fundamental properties (age, distance, and mass) of the stars in our sample. To improve target age determinations, we compiled and analyzed a complete set of age diagnostics.

Methods. We measured spectroscopic parameters and age diagnostics using dedicated observations acquired with FEROS and CORALIE spectrographs at La Silla Observatory. We also made extensive use of archival spectroscopic data and the results that are available in the literature. Additionally, we exploited photometric time-series, which are available in ASAS and Super-WASP archives, to derive a rotational period for a large fraction of our program stars.

Results. We provided updated characterization of all the targets observed in the VLT NaCo Large program, a survey designed to probe the occurrence of exoplanets and brown dwarfs in wide orbits. The median distance and age of our program stars are 64 pc and 100 Myr, respectively. Nearly all the stars have masses between 0.70 and 1.50 M_⊙, with a median value of 1.01 M_⊙. The typical metallicity is close to solar with a dispersion that is smaller than that of samples usually observed in radial velocity surveys. Several stars are confirmed or proposed here to be members of close young moving groups. Eight spectroscopic binaries are identified.