Letter to the Editor

Doppler tomography of transiting exoplanets: a prograde, low-inclined orbit for the hot Jupiter CoRoT-11b

¹ Research and Scientific Support Department, ESTEC/ESA, PO Box 299 2200 AG Noordwijk, The Netherlands
e-mail: davide.gandolfi@esa.int
² School of Physics & Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, UK
³ McDonald Observatory, University of Texas at Austin, Austin, TX 78712, USA
⁴ INAF – Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy
⁵ Laboratoire d’Astrophysique de Marseille, CNRS & University of Provence, 38 rue Frédéric Joliot-Curie, 13388 Marseille Cedex 13, France
⁶ Instituto de Astrofísica de Canarias, C/ Vía Láctea s/n, 38205 La Laguna, Spain
⁷ Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Spain
⁸ Thüringer Landessternwarte, Sternwarte 5, Tautenburg, 07778 Tautenburg, Germany

Received: 3 May 2012
Accepted: 12 June 2012

Abstract

We report the detection of the Doppler shadow of the transiting hot Jupiter CoRoT-11b. Our analysis is based on line-profile tomography of time-series, Keck/HIRES high-resolution spectra acquired during the transit of the planet. We measured a sky-projected, spin-orbit angle λ = 0.1°    ±    2.6°, which is consistent with a very low-inclined orbit with respect to the stellar rotation axis. We refined the physical parameters of the system using a Markov chain Monte Carlo simultaneous fitting of the available photometric and spectroscopic data. An analysis of the tidal evolution of the system shows how the currently measured obliquity and its uncertainty translate into an initial absolute value of less than about 10° on the zero-age main sequence, for an expected average modified tidal quality factor of the star ⟨ Q '_{* '} ⟩ ≳ 4 × 10⁶. This is indicative of an inward migration scenario that would not have perturbed the primordial low obliquity of CoRoT-11b. Taking into account the effective temperature and mass of the planet host star (T_eff = 6440 K, M_⋆ = 1.23 M_⊙), the system can be considered a new telling exception to the recently proposed trend, according to which relatively hot and massive stars (T_eff  >  6250 K, M_⋆  >  1.2 M_⊙) seem to be preferentially orbited by hot Jupiters with high obliquity.