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

The planet OGL E-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 x 10(5) < (Q(*)/k(2)) < 10(10). For values greater than Q(*)/k(2*) > 1.5 x 10(9) no 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(*)/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 x 10(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 x 10(7) < Q(*)/k(2*) < 1.5 x 10(9) if the system shall evolve significantly and realistically by tidal forces. (c) 2006 Published by Elsevier Ltd.