INTERPLAY of TIDAL EVOLUTION AND STELLAR WIND BRAKING IN THE ROTATION OF STARS HOSTING MASSIVE CLOSE-IN PLANETS

Abstract

This paper deals with the application of the creep tide theory (Ferraz-Mello) to the study of the rotation of stars hosting massive close-in planets. The stars have nearly the same tidal relaxation factors as gaseous planets and the evolution of their rotation is similar to that of close-in hot Jupiters: they tidally evolve toward a stationary solution. However, stellar rotation may also be affected by stellar wind braking. Thus, while the rotation of a quiet host star evolves toward a stationary attractor with a frequency (1 + 6e 2 ) times the orbital mean motion of the companion the continuous loss of angular momentum in an active star displaces the stationary solution toward slower values: active host stars with big close-in companions tend to have rotational periods longer than the orbital periods of their companions. The study of some hypothetical examples shows that, because of tidal evolution, the rules of gyrochronology cannot be used to estimate the age of one system with a large close-in companion, no matter if the star is quiet or active, if the current semimajor axis of the companion is smaller than 0.03-0.04 AU. Details on the evolution of the systems: CoRoT LRc06E21637, CoRoT-27, Kepler-75 CoRoT-2, CoRoT-18, CoRoT-14 and on hypothetical systems with planets of mass 1-4 M Jup in orbit around a star similar to the Sun are given.