Volume 575, March 2015
|Number of page(s)||8|
|Section||Planets and planetary systems|
|Published online||24 February 2015|
WASP-20b and WASP-28b: a hot Saturn and a hot Jupiter in near-aligned orbits around solar-type stars ⋆,⋆⋆
1 Astrophysics Group, Keele University, Staffordshire ST5 5BG, UK
2 SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, Fife KY16 9SS, UK
3 Observatoire de Genève, Université de Genève, 51 Chemin des Maillettes, 1290 Sauverny, Switzerland
4 Las Cumbres Observatory Global Telescope Network, 6740 Cortona Dr. Suite 102, Goleta, CA 93117, USA
5 Cavendish Laboratory, J J Thomson Avenue, Cambridge, CB3 0HE, UK
6 N. Copernicus Astronomical Centre, Polish Academy of Sciences, Bartycka 18, 00-716 Warsaw, Poland
7 Department of Physics, and Kavli Institute for Astrophysics and Space Research, MIT, Cambridge, MA 02139, USA
8 Department of Physics, University of Warwick, Coventry CV4 7AL, UK
9 Astrophysics Research Centre, School of Mathematics & Physics, Queen’s University, University Road, Belfast BT7 1NN, UK
10 Institut d’Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août, 17, Bât. B5C, Liège 1, Belgium
Received: 6 February 2014
Accepted: 5 December 2014
We report the discovery of the planets WASP-20b and WASP-28b along with measurements of their sky-projected orbital obliquities. WASP-20b is an inflated, Saturn-mass planet (0.31 MJup; 1.46 RJup) in a 4.9-day, near-aligned (λ = 12.7 ± 4.2°) orbit around CD-24 102 (V = 10.7; F9). Due to the low density of the planet and the apparent brightness of the host star, WASP-20 is a good target for atmospheric characterisation via transmission spectroscopy. WASP-28b is an inflated, Jupiter-mass planet (0.91 MJup; 1.21 RJup) in a 3.4-day, near-aligned (λ = 8 ± 18°) orbit around a V = 12, F8 star. As intermediate-mass planets in short orbits around aged, cool stars (7+ 2-1 Gyr and 6000 ± 100 K for WASP-20; 5+ 3-2 Gyr and 6100 ± 150 K for WASP-28), their orbital alignment is consistent with the hypothesis that close-in giant planets are scattered into eccentric orbits with random alignments, which are then circularised and aligned with their stars’ spins via tidal dissipation.
Key words: planetary systems / stars: individual: WASP-20b / stars: individual: WASP-28b
Based on observations made with: the WASP-South (South Africa) and SuperWASP-North (La Palma) photometric survey instruments; the C2 and EulerCam cameras and the CORALIE spectrograph, all mounted on the 1.2-m Euler-Swiss telescope (La Silla); the HARPS spectrograph on the ESO 3.6-m telescope (La Silla) under programs 072.C-0488, 082.C-0608, 084.C-0185, and 085.C-0393; and LCOGT’s Faulkes Telescope North (Maui) and Faulkes Telescope South (Siding Spring).
Full Tables 2 and 3 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (188.8.131.52) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A61
© ESO, 2015
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