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First light of the VLT planet finder SPHERE IV. Physical and chemical properties of the planet around HR8799

Bonnefoy, M. and Mawet, D. (2016) First light of the VLT planet finder SPHERE IV. Physical and chemical properties of the planet around HR8799. Astronomy and Astrophysics, 587 . Art. No. A58. ISSN 0004-6361. doi:10.1051/0004-6361/201526906.

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Context. The system of fourplanets discovered around the intermediate-mass star HR8799 offers a unique opportunity to test planet formation theories at large orbital radii and to probe the physics and chemistry at play in the atmospheres of self-luminous young (~30 Myr) planets. We recently obtained new photometry of the four planets and low-resolution (R ~ 30) spectra of HR8799 d and e with the SPHERE instrument (Paper III). Aims. In this paper (Paper IV), we aim to use these spectra and available photometry to determine how they compare to known objects, what the planet physical properties are, and how their atmospheres work. Methods. We compare the available spectra, photometry, and spectral energy distribution (SED) of the planets to field dwarfs and young companions. In addition, we use the extinction from corundum, silicate (enstatite and forsterite), or iron grains likely to form in the atmosphere of the planets to try to better understand empirically the peculiarity of their spectrophotometric properties. To conclude, we use three sets of atmospheric models (BT-SETTL14, Cloud-AE60, Exo-REM) to determine which ingredients are critically needed in the models to represent the SED of the objects, and to constrain their atmospheric parameters (T_(eff), log g, M/H). Results. We find that HR8799d and e properties are well reproduced by those of L6-L8 dusty dwarfs discovered in the field, among which some are candidate members of young nearby associations. No known object reproduces well the properties of planets b and c. Nevertheless, we find that the spectra and WISE photometry of peculiar and/or young early-T dwarfs reddened by submicron grains made of corundum, iron, enstatite, or forsterite successfully reproduce the SED of these planets. Our analysis confirms that only the Exo-REM models with thick clouds fit (within 2σ) the whole set of spectrophotometric datapoints available for HR8799 d and e for T_(eff) = 1200 K, log g in the range 3.0−4.5, and M/H = +0.5. The models still fail to reproduce the SED of HR8799c and b. The determination of the metallicity, log g, and cloud thickness are degenerate. Conclusions. Our empirical analysis and atmospheric modelling show that an enhanced content in dust and decreased CIA of H_2 is certainly responsible for the deviation of the properties of the planet with respect to field dwarfs. The analysis suggests in addition that HR8799c and b have later spectral types than the two other planets, and therefore could both have lower masses.

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Bonnefoy, M.0000-0001-5579-5339
Mawet, D.0000-0002-8895-4735
Additional Information:© 2016 ESO. Received 6 July 2015. Accepted 13 September 2015. We are grateful to the SPHERE team and all the people at Paranal for the great effort during SPHERE commissioning runs. We thank Rebecca Oppenheimer, Laurent Pueyo, and Travis Barman for providing an access to their spectra of the HR8799 planets. We also thank P. Ingraham, G. Mace, J. Gizis, M. Liu, A. Schneider, D. Stephens, M. Cushing, B. Bowler, D. Kirkpatrick, P. Rojo, K. Allers, J. Patience, M.-E. Naud, and B. Gauza for sending us their spectra of young companions and dusty dwarfs. This research has benefitted from the SpeX Prism Spectral Libraries, maintained by Adam Burgasser at M.B., G.Ch, A.-M.L., J.-L.B., F.A., D.H. and D.M. acknowledge support from the French National Research Agency (ANR) through the GUEPARD project grant ANR10-BLANC0504-01 and from the Programmes Nationaux de Planétologie et de Physique Stellaire (PNP & PNPS, CNRS/INSU). A.Z., D.M., R.G., R.C., and S.D. acknowledge partial support from PRIN INAF 2010 “Planetary systems at young ages”. A.Z., D.M., A.-L.M., R.G., S.D., and R.U.C. acknowledge support from the “Progetti Premiali” funding scheme of the Italian Ministry of Education, University, and Research. A.Z. acknowledges support from the MillenniumvScience Initiative (Chilean Ministry of Economy), through grant “Nucleus RC130007”. SPHERE is an instrument designed and built by a consortium consisting of IPAG (Grenoble, France), MPIA (Heidelberg, Germany), LAM (Marseille, France), LESIA (Paris, France), Laboratoire Lagrange (Nice, France), INAF Osservatorio di Padova (Italy), Observatoire de Genève (Switzerland), ETH Zurich (Switzerland), NOVA (The Netherlands), ONERA (France) and ASTRON (The Netherlands), in collaboration with ESO. SPHERE was funded by ESO, with additional contributions from CNRS (France), MPIA (Germany), INAF (Italy), FINES (Switzerland) and NOVA (The Netherlands). SPHERE also received funding from the European Commission Sixth and Seventh Framework Programmes as part of the Optical Infrared Coordination Network for Astronomy (OPTICON) under grant No. RII3-Ct-2004-001566 for FP6 (2004–2008), grant No. 226604 for FP7 (2009–2012) and grant No. 312430 for FP7 (2013–2016). D.H. acknowledges support from the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007–2013 Grant Agreement No. 247060) and from the Collaborative Research Centre SFB 881 “The Milky Way System” (subproject A4) of the German Research Foundation (DFG).
Funding AgencyGrant Number
Agence Nationale de la Recherche (ANR)ANR10-BLANC0504-01
Programmes Nationaux de Planétologie et de Physique Stellaire (PNP & PNPS)UNSPECIFIED
Institut national des sciences de l'Univers (INSU)UNSPECIFIED
Ministero dell'Istruzione, dell'Università e della Ricerca (MIUR)UNSPECIFIED
Millennium Science Initiative (Chilean Ministry of Economy)Nucleus RC130007
European Southern Observatory (ESO)UNSPECIFIED
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Max Planck Institute for Astronomy (MPIA)UNSPECIFIED
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
European Commission Sixth and Seventh Framework ProgrammesUNSPECIFIED
Optical Infrared Coordination Network for Astronomy (OPTICON)RII3-Ct- 2004-001566
European Research Council (ERC)226604
European Research Council (ERC)312430 (OPTICON)
European Research Council (ERC)247060
Deutsche Forschungsgemeinschaft (DFG)SFB 881
Subject Keywords:instrumentation: high angular resolution – stars: individual: HR8799 – planets and satellites: atmospheres – planets and satellites: detection – techniques: imaging spectroscopy – planets and satellites: fundamental parameters
Record Number:CaltechAUTHORS:20160502-071114068
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Official Citation:First light of the VLT planet finder SPHERE - IV. Physical and chemical properties of the planets around HR8799 M. Bonnefoy, A. Zurlo, J. L. Baudino, P. Lucas, D. Mesa, A.-L. Maire, A. Vigan, R. Galicher, D. Homeier, F. Marocco, R. Gratton, G. Chauvin, F. Allard, S. Desidera, M. Kasper, C. Moutou, A.-M. Lagrange, J. Antichi, A. Baruffolo, J. Baudrand, J.-L. Beuzit, A. Boccaletti, F. Cantalloube, M. Carbillet, J. Charton, R. U. Claudi, A. Costille, K. Dohlen, C. Dominik, D. Fantinel, P. Feautrier, M. Feldt, T. Fusco, P. Gigan, J. H. Girard, L. Gluck, C. Gry, T. Henning, M. Janson, M. Langlois, F. Madec, Y. Magnard, D. Maurel, D. Mawet, M. R. Meyer, J. Milli, O. Moeller-Nilsson, D. Mouillet, A. Pavlov, D. Perret, P. Pujet, S. P. Quanz, S. Rochat, G. Rousset, A. Roux, B. Salasnich, G. Salter, J.-F. Sauvage, H. M. Schmid, A. Sevin, C. Soenke, E. Stadler, M. Turatto, S. Udry, F. Vakili, Z. Wahhaj and F. Wildi A&A, 587 (2016) A58 DOI:
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ID Code:66568
Deposited By: Ruth Sustaita
Deposited On:03 May 2016 17:57
Last Modified:10 Nov 2021 23:59

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