[en] 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 M[SUB]Jup[/SUB]; 1.46 R[SUB]Jup[/SUB]) 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 M[SUB]Jup[/SUB]; 1.21 R[SUB]Jup[/SUB]) 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[SUP]+ 2[/SUP][SUB]-1[/SUB] Gyr and 6000 ± 100 K for WASP-20; 5[SUP]+ 3[/SUP][SUB]-2[/SUB] 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. 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 <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A61">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A61</A>
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Anderson, D. R.; Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
Collier Cameron, A.; SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, Fife, KY16 9SS, UK
Hellier, C.; Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
Lendl, Monika ; Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa)
Lister, T. A.; Las Cumbres Observatory Global Telescope Network, 6740 Cortona Dr. Suite 102, Goleta, CA, 93117, USA
Maxted, P. F. L.; Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
Queloz, D.; Observatoire de Genève, Université de Genève, 51 Chemin des Maillettes, 1290, Sauverny, Switzerland ; Cavendish Laboratory, J J Thomson Avenue, Cambridge, CB3 0HE, UK
Smalley, B.; Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
Smith, A. M. S.; Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK ; N. Copernicus Astronomical Centre, Polish Academy of Sciences, Bartycka 18, 00-716, Warsaw, Poland
Triaud, A. H. M. J.; Observatoire de Genève, Université de Genève, 51 Chemin des Maillettes, 1290, Sauverny, Switzerland ; Department of Physics, and Kavli Institute for Astrophysics and Space Research, MIT, Cambridge, MA, 02139, USA
Brown, D. J. A.; Department of Physics, University of Warwick, Coventry, CV4 7AL, UK ; Astrophysics Research Centre, School of Mathematics & Physics, Queen's University, University Road, Belfast, BT7 1NN, UK
Gillon, Michaël ; Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa)
Neveu-VanMalle, M.; Observatoire de Genève, Université de Genève, 51 Chemin des Maillettes, 1290, Sauverny, Switzerland
Pepe, F.; Observatoire de Genève, Université de Genève, 51 Chemin des Maillettes, 1290, Sauverny, Switzerland
Pollacco, D.; Department of Physics, University of Warwick, Coventry, CV4 7AL, UK
Ségransan, D.; Observatoire de Genève, Université de Genève, 51 Chemin des Maillettes, 1290, Sauverny, Switzerland
Udry, S.; Observatoire de Genève, Université de Genève, 51 Chemin des Maillettes, 1290, Sauverny, Switzerland
West, R. G.; Department of Physics, University of Warwick, Coventry, CV4 7AL, UK
Wheatley, P. J.; Department of Physics, University of Warwick, Coventry, CV4 7AL, UK)
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