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*Q* and the stellar love number k2,*k2,*of the star, which is only poorly known and estimates range within 5×105<(Q*/k2*)<10105×105<(Q*/k2*)<1010. For values greater than Q*/k2*>1.5×109Q*/k2*>1.5×109no observable influence by tidal forces on the planet's orbit within the lifetime for the star can be found. A lower limit for the possible values of the parameter Q*/k2*Q*/k2*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*/k2*<2×107Q*/k2*<2×107, which is not in agreement with observed stellar rotation periods. From a statistical analysis based on a Monte-Carlo tidal evolution simulation, the Q*/k2*Q*/k2* parameter can be constrained to the range 2×107