The GAPS programme with HARPS-N at TNG^⋆

I. Observations of the Rossiter-McLaughlin effect and characterisation of the transiting system Qatar-1^{⋆⋆,⋆⋆⋆}

¹ INAF – Osservatorio Astronomico di Capodimonte, via Moiariello, 16, 80131 Naples, Italy
e-mail: covino@oacn.inaf.it
² Instituto de Astrofísica de Canarias, C/ vía Láctea, s/n, 38205 La Laguna (Tenerife), Spain
³ Dipartimento di Fisica e Astronomia Galileo Galilei, Università di Padova, Vicolo dell’Osservatorio 2, 35122 Padova, Italy
⁴ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁵ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁶ INAF – Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy
⁷ INAF – Osservatorio Astrofisico di Torino, via Osservatorio 20, 10025 Pino Torinese, Italy
⁸ INAF – Osservatorio Astronomico di Palermo, Piazza del Parlamento, Italy 1, 90134 Palermo, Italy
⁹ Research and Scientific Support Department, ESTEC/ESA, PO Box 299, 2200 AG Noordwijk, The Netherlands
¹⁰ SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, Fife KY16 9SS, UK
¹¹ Fundación Galileo Galilei − INAF, Rambla José Ana Fernandez Pérez, 7 38712 Breña Baja, TF, Spain
¹² INAF – IASF Milano, via Bassini 15, 20133 Milano, Italy
¹³ Observatoire Astronomique de l’Université de Geneve, 51 Ch. des Maillettes, Sauverny, 1290 Versoix, Switzerland
¹⁴ Institut de Ciències de l’Espai (CSIC-IEEC), Campus UAB, Facultat de Ciències, Torre C5 parell, 2a pl, 08193 Bellaterra, Spain
¹⁵ Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
¹⁶ Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Portugal
¹⁷ Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
¹⁸ Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
¹⁹ Departamento de Astrofísica, Universidad de La Laguna, Avda. Astrofísico Francisco Sánchez, s/n 38206 La Laguna, Tenerife, Spain
²⁰ INAF – Osservatorio Astronomico di Brera, via E. Bianchi 46, 23807 Merate (LC), Italy
²¹ Institut d’Astrophysique de Paris, UMR 7095 CNRS, Université Pierre & Marie Curie, 98bis boulevard Arago, 75014 Paris, France
²² INAF – Osservatorio Astronomico di Trieste, via Tiepolo 11, 34143 Trieste Italy
²³ Lowell Observatory, 1400 W. Mars Hill Road, Flagstaff, AZ 86001, USA
²⁴ Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
²⁵ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
²⁶ Università dell’Insubria − Dipartimento di Scienza e Alta Tecnologia, via Valleggio 11, 22100 Como, Italy
²⁷ Osservatorio Astronomico della Regione Autonoma Valle d’Aosta, Fraz. Lignan 39, 11020 Nus (Aosta), Italy
²⁸ INAF Istituto di Fisica e Planetologia Spaziali, via Fosso del Cavaliere 100, 00133 Roma, Italy
²⁹ Dipartimento di Fisica dell’Universitá degli studi di Milano, via Celoria, 16, 20133 Milano, Italy

Received: 14 February 2013
Accepted: 28 March 2013

Abstract

Context. Our understanding of the formation and evolution of planetary systems is still fragmentary because most of the current data provide limited information about the orbital structure and dynamics of these systems. The knowledge of the orbital properties for a variety of systems and at different ages yields information on planet migration and on star-planet tidal interaction mechanisms.

Aims. In this context, a long-term, multi-purpose, observational programme has started with HARPS-N at TNG and aims to characterise the global architectural properties of exoplanetary systems. The goal of this first paper is to fully characterise the orbital properties of the transiting system Qatar-1 as well as the physical properties of the star and the planet.

Methods. We exploit HARPS-N high-precision radial velocity measurements obtained during a transit to measure the Rossiter-McLaughlin effect in the Qatar-1 system, and out-of-transit measurements to redetermine the spectroscopic orbit. New photometric-transit light-curves were analysed and a spectroscopic characterisation of the host star atmospheric parameters was performed based on various methods (line equivalent width ratios, spectral synthesis, spectral energy distribution).

Results. We achieved a significant improvement in the accuracy of the orbital parameters and derived the spin-orbit alignment of the system; this information, combined with the spectroscopic determination of the host star properties (rotation, T_eff, log g, metallicity), allows us to derive the fundamental physical parameters for star and planet (masses and radii). The orbital solution for the Qatar-1 system is consistent with a circular orbit and the system presents a sky-projected obliquity of λ =  − 8.4 ± 7.1 deg. The planet, with a mass of 1.33 ± 0.05 M_J, is found to be significantly more massive than previously reported. The host star is confirmed to be metal-rich ([Fe/H] = 0.20 ± 0.10) and slowly rotating (vsinI = 1.7 ± 0.3 km s^-1), though moderately active, as indicated by the strong chromospheric emission in the Ca ii H&K line cores (log R'_HK ≈ -4.60).

Conclusions. We find that the system is well aligned and fits well within the general λ versus T_eff trend. We can definitely rule out any significant orbital eccentricity. The evolutionary status of the system is inferred based on gyrochronology, and the present orbital configuration and timescale for orbital decay are discussed in terms of star-planet tidal interactions.