Constraints on the tidal dissipation factor of a main sequence star: The case of OGLE-TR-56b

The planet OGLE-TR-56b is the extrasolar giant planet closest to its host star. This planet and its star exchange extreme tidal forces. This leads to a reduction of the planetary orbit and a spin-up of the stellar rotation. The tidal migration rate depends crucially on the ratio of the tidal dissipation factor Q * and the stellar love number k 2 , * of the star, which is only poorly known and estimates range within 5 × 1 0 5 < ( Q * / k 2 * ) < 1 0 10 . For values greater than Q * / k 2 * > 1.5 × 1 0 9 no observable influence by tidal forces on the planetʹs orbit within the lifetime for the star can be found. A lower limit for the possible values of the parameter Q * / k 2 * for the G-type star OGLE-TR-56 was found by studying the evolution of possible tidal interaction into the future and in the past. This study demonstrates that on the basis of conservative model assumptions, a considerable but unrealistic spin-up of the star can be expected if Q * / k 2 * < 2 × 1 0 7 , which is not in agreement with observed stellar rotation periods. From a statistical analysis based on a Monte-Carlo tidal evolution simulation, the Q * / k 2 * parameter can be constrained to the range 2 × 1 0 7 < Q * / k 2 * < 1.5 × 1 0 9 if the system shall evolve significantly and realistically by tidal forces.