Volume 533, September 2011
|Number of page(s)||14|
|Section||Planets and planetary systems|
|Published online||15 September 2011|
XVIII. CoRoT-18b: a massive hot Jupiter on a prograde, nearly aligned orbit
Institut d’Astrophysique de Paris, UMR7095 CNRS, Université Pierre
& Marie Curie, 98bis
boulevard Arago, 75014
2 Observatoire de Haute-Provence, CNRS/OAMP, 04870 Saint-Michel-l’Observatoire, France
3 Department of Physics, Denys Wilkinson Building Keble Road, Oxford, OX1 3RH, UK
4 Observatoire de l’Université de Genève, 51 chemin des Maillettes, 1290 Sauverny, Switzerland
5 Research and Scientific Support Department, European Space Agency, Keplerlaan1, 2200AG Noordwijk, The Netherlands
6 School of Physics and Astronomy, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, Israel
7 Observatoire de la Côte d’Azur, Laboratoire Cassiopée, BP 4229, 06304 Nice Cedex 4, France
8 Laboratoire d’Astrophysique de Marseille, 38 rue Frédéric Joliot-Curie, 13388 Marseille Cedex 13, France
9 Instituto de Astrofísica de Canarias, and Universidad de La Laguna, Dept. de Astrofísica, 38205 La Laguna, Tenerife, Spain
10 LESIA, Observatoire de Paris, Place J. Janssen, 92195 Meudon Cedex, France
11 Institut d’Astrophysique Spatiale, Université Paris XI, 91405 Orsay, France
12 Institute of Planetary Research, German Aerospace Center, Rutherfordstrasse 2, 12489 Berlin, Germany
13 Rheinisches Institut für Umweltforschung an der Universität zu Köln, Aachener Strasse 209, 50931, Germany
14 University of Vienna, Institute of Astronomy, Türkenschanzstr. 17, 1180 Vienna, Austria
15 IAG, Universidade de Sao Paulo, Brazil
16 University of Liège, Allée du 6 août 17, Sart Tilman, Liège 1, Belgium
17 Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
18 Space Research Institute, Austrian Academy of Science, Schmiedlstr. 6, 8042 Graz, Austria
19 Center for Astronomy and Astrophysics, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
20 LUTH, Observatoire de Paris, CNRS, Université Paris Diderot, 5 place Jules Janssen, 92195 Meudon, France
Received: 4 May 2011
Accepted: 7 July 2011
We report the detection of CoRoT-18b, a massive hot Jupiter transiting in front of its host star with a period of 1.9000693 ± 0.0000028 days. This planet was discovered thanks to photometric data secured with the CoRoT satellite combined with spectroscopic and photometric ground-based follow-up observations. The planet has a mass Mp = 3.47 ± 0.38 MJup, a radius Rp = 1.31 ± 0.18 RJup, and a density ρp = 2.2 ± 0.8 g cm-3. It orbits a G9V star with a mass M⋆ = 0.95 ± 0.15 M⊙, a radius R⋆ = 1.00 ± 0.13 R⊙, and arotation period Prot = 5.4 ± 0.4 days. The age of the system remains uncertain, with stellar evolution models pointing either to a few tens Ma or several Ga, while gyrochronology and lithium abundance point towards ages of a few hundred Ma. This mismatch potentially points to a problem in our understanding of the evolution of young stars, with possibly significant implications for stellar physics and the interpretation of inferred sizes of exoplanets around young stars. We detected the Rossiter-McLaughlin anomaly in the CoRoT-18 system thanks to the spectroscopic observation of a transit. We measured the obliquity ψ = 20° ± 20° (sky-projected value λ = −10° ± 20°), indicating that the planet orbits in the same way as the star is rotating and that this prograde orbit is nearly aligned with the stellar equator.
Key words: planetary systems / techniques: spectroscopic / techniques: photometric / techniques: radial velocities
The CoRoT space mission, launched on 2006 December 27, has been developed and is operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA (RSSD and Science Programme), Germany and Spain.
Table 2 is available in electronic form at http://www.aanda.org
© ESO, 2011
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