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Thermal emission at 4.5 and 8 μm of WASP-17b, an extremely large planet in a slightly eccentric orbit

Anderson, D. R. ; Smith, A. M. S. ; Lanotte, A. A. ; Barman, T. S. ; Cameron, A. Collier ; Campo, C. J. ; Gillon, M. ; Harrington, J. ; Hellier, C. ; Maxted, P. F. L. ; Queloz, D. ; Triaud, A. H. M. J. ; Wheatley, P. J.

In: Monthly Notices of the Royal Astronomical Society, 2011, vol. 416, no. 3, p. 2108-2122

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    Titre
    • Thermal emission at 4.5 and 8 μm of WASP-17b, an extremely large planet in a slightly eccentric orbit
    Auteur
    • Anderson, D. R.. Astrophysics Group, Keele University, Staffordshire ST5 5BG
    • Smith, A. M. S.. Astrophysics Group, Keele University, Staffordshire ST5 5BG
    • Lanotte, A. A.. Institut d'Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août 17, Bat. B5C, Liège 1, Belgium
    • Barman, T. S.. Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001, USA
    • Cameron, A. Collier. SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS
    • Campo, C. J.. Planetary Sciences Group, Department of Physics, University of Central Florida, Orlando, FL 32816-2385, USA
    • Gillon, M.. Institut d'Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août 17, Bat. B5C, Liège 1, Belgium
    • Harrington, J.. Planetary Sciences Group, Department of Physics, University of Central Florida, Orlando, FL 32816-2385, USA
    • Hellier, C.. Astrophysics Group, Keele University, Staffordshire ST5 5BG
    • Maxted, P. F. L.. Astrophysics Group, Keele University, Staffordshire ST5 5BG
    • Queloz, D.. Observatoire de Genève, Université de Genève, 51 Chemin des Maillettes, 1290 Sauverny, Switzerland
    • Triaud, A. H. M. J.. Observatoire de Genève, Université de Genève, 51 Chemin des Maillettes, 1290 Sauverny, Switzerland
    • Wheatley, P. J.. Department of Physics, University of Warwick, Coventry CV4 7AL
    Type de document
    • Postprint
    Langue
    • Anglais
    Publié dans
    • Monthly Notices of the Royal Astronomical Society, 2011, vol. 416, no. 3, p. 2108-2122. Blackwell Publishing Ltd
    Autre version électronique
    Identifiant OAI-PMH
    • oai:doc.rero.ch:290449
    Summary
    We report the detection of thermal emission at 4.5 and 8 μm from the planet WASP-17b. We used Spitzer to measure the system brightness at each wavelength during two occultations of the planet by its host star. By combining the resulting light curves with existing transit light curves and radial-velocity measurements in a simultaneous analysis, we find the radius of WASP-17b to be 2.0RJup, which is 0.2RJup larger than any other known planet and 0.7RJup larger than predicted by the standard cooling theory of irradiated gas giant planets. We find the retrograde orbit of WASP-17b to be slightly eccentric, with 0.0012 < e < 0.070 (3σ). Such a low eccentricity suggests that, under current models, tidal heating alone could not have bloated the planet to its current size, so the radius of WASP-17b is currently unexplained. From the measured planet-star flux-density ratios we infer 4.5 and 8 μm brightness temperatures of 1881 ± 50 and 1580 ± 150 K, respectively, consistent with a low-albedo planet that efficiently redistributes heat from its day side to its night side