%0 Journal Article
%T The retrograde orbit of the HAT-P-6b exoplanet
%A G. Hebrard
%A D. Ehrenreich
%A F. Bouchy
%A X. Delfosse
%A C. Moutou
%A L. Arnold
%A I. Boisse
%A X. Bonfils
%A R. F. Diaz
%A A. Eggenberger
%A T. Forveille
%A A. -M. Lagrange
%A C. Lovis
%A F. Pepe
%A C. Perrier
%A D. Queloz
%A A. Santerne
%A N. C. Santos
%A D. Segransan
%A S. Udry
%A A. Vidal-Madjar
%J Physics
%D 2011
%I arXiv
%R 10.1051/0004-6361/201016331
%X We observed with the SOPHIE spectrograph (OHP, France) the transit of the HAT-P-6b exoplanet across its host star. The resulting stellar radial velocities display the Rossiter-McLaughlin anomaly and reveal a retrograde orbit: the planetary orbital spin and the stellar rotational spin point towards approximately opposite directions. A fit to the anomaly measures a sky-projected angle lambda = 166 +/- 10 degrees between these two spin axes. All seven known retrograde planets are hot jupiters with masses M_p < 3 M_Jup. About two thirds of the planets in this mass range however are prograde and aligned (lambda ~ 0). By contrast, most of the more massive planets (M_p > 4 M_Jup) are prograde but misaligned. Different mechanisms may therefore be responsible for planetary obliquities above and below ~3.5 M_Jup.
%U http://arxiv.org/abs/1101.5009v1