stars: individual: 51 Eridani; planets and satellites: atmospheres; methods: data analysis; techniques: high angular resolution; techniques: image processing; Astrophysics - Earth and Planetary Astrophysics
Abstract :
[en] Context. 51 Eridani b is an exoplanet around a young (20 Myr) nearby (29.4 pc) F0-type star, which was recently discovered by direct imaging. It is one of the closest direct imaging planets in angular and physical separation ( 0.5'', 13 au) and is well suited for spectroscopic analysis using integral field spectrographs. <BR /> Aims: We aim to refine the atmospheric properties of the known giant planet and to constrain the architecture of the system further by searching for additional companions. <BR /> Methods: We used the extreme adaptive optics instrument SPHERE at the Very Large Telescope (VLT) to obtain simultaneous dual-band imaging with IRDIS and integral field spectra with IFS, extending the spectral coverage of the planet to the complete Y- to H-band range and providing additional photometry in the K12-bands (2.11, 2.25 μm). The object is compared to other known cool and peculiar dwarfs. The posterior probability distributions for parameters of cloudy and clear atmospheric models are explored using MCMC. We verified our methods by determining atmospheric parameters for the two benchmark brown dwarfs Gl 570D and HD 3651B. We used archival VLT-NACO (L') Sparse Aperture Masking data to probe the innermost region for additional companions. <BR /> Results: We present the first spectrophotometric measurements in the Y and K bands for the planet and revise its J-band flux to values 40% fainter than previous measurements. Cloudy models with uniform cloud coverage provide a good match to the data. We derive the temperature, radius, surface gravity, metallicity, and cloud sedimentation parameter f[SUB]sed[/SUB]. We find that the atmosphere is highly super-solar ([Fe/H] = 1.0 ± 0.1 dex), and the low f[SUB]sed[/SUB] = 1.26[SUP]+0.36[/SUP][SUB]-0.29[/SUB] value is indicative of a vertically extended, optically thick cloud cover with small sized particles. The model radius and surface gravity estimates suggest higher planetary masses of M[SUB]gravity[/SUB] = 9.1[SUP]+4.9[/SUP][SUB]-3.3[/SUB] M[SUB]J[/SUB]. The evolutionary model only provides a lower mass limit of > 2 M[SUB]J[/SUB] (for pure hot- start). The cold-start model cannot explain the luminosity of the planet. The SPHERE and NACO/SAM detection limits probe the 51 Eri system at solar system scales and exclude brown-dwarf companions more massive than 20 M[SUB]J[/SUB] beyond separations of 2.5 au and giant planets more massive than 2 M[SUB]J[/SUB] beyond 9 au. <P />Based on observations made with ESO Telescopes at the Paranal Observatory under program ID 095.C-0298, 096.C-0241 and 084.C-0739(A).Spectra, covariances, and petitCODE (fits files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/603/A57
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Samland, M.; Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany ; International Max Planck Research School for Astronomy and Cosmic Physics at the University of Heidelberg (IMPRS-HD), 69117, Heidelberg, Germany
Mollière, P.; Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany ; International Max Planck Research School for Astronomy and Cosmic Physics at the University of Heidelberg (IMPRS-HD), 69117, Heidelberg, Germany
Bonnefoy, M.; Univ. Grenoble Alpes, CNRS, IPAG, 38000, Grenoble, France
Biller, B. A.; Institute for Astronomy, University of Edinburgh, Blackford Hill View, Edinburgh, EH9 3HJ, UK ; Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany
Wahhaj, Z.; European Southern Observatory, Alonso de Cordova 3107, Casilla 19001 Vitacura, Santiago 19, Chile
Bouwman, J.; Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany
Brandner, W.; Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany
Melnick, D.; Department of Physics & Astronomy, College of Charleston, 66 George Street, Charleston, SC, 29424, USA
Carson, J.; Department of Physics & Astronomy, College of Charleston, 66 George Street, Charleston, SC, 29424, USA ; Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany
Janson, M.; Department of Astronomy, Stockholm University, AlbaNova University Center, 106 91, Stockholm, Sweden ; Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany
Henning, T.; Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany
Homeier, D.; Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Königstuhl 12, 69117, Heidelberg, Germany
Mordasini, C.; Physikalisches Institut, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
Langlois, M.; CRAL, UMR 5574, CNRS, Université Lyon 1, 9 avenue Charles André, 69561, Saint Genis Laval Cedex, France ; Aix-Marseille Univ., CNRS, LAM, Laboratoire d'Astrophysique de Marseille, 13013, Marseille, France
Quanz, S. P.; Institute for Astronomy, ETH Zurich, Wolfgang-Pauli-Strasse 27, 8093, Zurich, Switzerland
van Boekel, R.; Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany
Zurlo, A.; Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile ; Núcleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile ; Aix-Marseille Univ., CNRS, LAM, Laboratoire d'Astrophysique de Marseille, 13013, Marseille, France
Schlieder, J. E.; NASA Ames Research Center, Moffett Field, CA, 94035, USA ; Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany
Avenhaus, H.; Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile ; Núcleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile ; Institute for Astronomy, ETH Zurich, Wolfgang-Pauli-Strasse 27, 8093, Zurich, Switzerland
Beuzit, J.-L.; Univ. Grenoble Alpes, CNRS, IPAG, 38000, Grenoble, France
Boccaletti, A.; LESIA, Observatoire de Paris, PSL Research Univ., CNRS, Univ. Paris Diderot, Sorbonne Paris Cité, UPMC Paris 6, Sorbonne Univ., 5 place Jules Janssen, 92195, Meudon Cedex, France
Bonavita, M.; Institute for Astronomy, University of Edinburgh, Blackford Hill View, Edinburgh, EH9 3HJ, UK ; INAF-Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122, Padova, Italy
Chauvin, G.; Univ. Grenoble Alpes, CNRS, IPAG, 38000, Grenoble, France
Feldt, M.; Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany
Fusco, T.; ONERA, The French Aerospace Lab BP72, 29 avenue de la Division Leclerc, 92322, Châtillon Cedex, France
Galicher, R.; LESIA, Observatoire de Paris, PSL Research Univ., CNRS, Univ. Paris Diderot, Sorbonne Paris Cité, UPMC Paris 6, Sorbonne Univ., 5 place Jules Janssen, 92195, Meudon Cedex, France
Kopytova, T. G.; Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany ; International Max Planck Research School for Astronomy and Cosmic Physics at the University of Heidelberg (IMPRS-HD), 69117, Heidelberg, Germany ; School of Earth & Space Exploration, Arizona State University, Tempe, AZ, 85287, USA ; Ural Federal University, 620002, Yekaterinburg, Russia
Lagrange, A.-M.; Univ. Grenoble Alpes, CNRS, IPAG, 38000, Grenoble, France
Le Coroller, H.; Aix-Marseille Univ., CNRS, LAM, Laboratoire d'Astrophysique de Marseille, 13013, Marseille, France
Martinez, P.; Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Lagrange, 06304, Nice Cedex 4, France
Moeller-Nilsson, O.; Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany
Mouillet, D.; Univ. Grenoble Alpes, CNRS, IPAG, 38000, Grenoble, France
Mugnier, L. M.; ONERA, The French Aerospace Lab BP72, 29 avenue de la Division Leclerc, 92322, Châtillon Cedex, France
Perrot, C.; LESIA, Observatoire de Paris, PSL Research Univ., CNRS, Univ. Paris Diderot, Sorbonne Paris Cité, UPMC Paris 6, Sorbonne Univ., 5 place Jules Janssen, 92195, Meudon Cedex, France
Sevin, A.; LESIA, Observatoire de Paris, PSL Research Univ., CNRS, Univ. Paris Diderot, Sorbonne Paris Cité, UPMC Paris 6, Sorbonne Univ., 5 place Jules Janssen, 92195, Meudon Cedex, France
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