Orbital evolution of circumbinary planets due to creep tides

FEDERICO ZOPPETTI; FOLONIER, H.; ALEJANDRO MARTÍN LEIVA; GABRIEL GOMES

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Año: 2022

0004-6361

Most confirmed circumbinary planets are located very close to their host binary where the tidal forces are expected to play an importantrole in their dynamics. Here we consider the orbital evolution of a circumbinary planet with arbitrary viscosity, subjected to tides dueto both central stars. We adopt the creep tide theory and assume that the planet is the only extended body in the system and that itsorbital evolution occurs after acquiring its pseudo-synchronous stationary rotational state. With this aim, we first performed a set ofnumerical integrations of the tidal equations, using a Kepler 38-type system as a working example. For this case we find that theamount of planetary tidal migration and also, curiously, its direction both depend on the viscosity. However, the effect of tides onits eccentricity and pericenter evolutions is simply a move toward pure gravitational secular solutions. Then we present a secularanalytical model for the planetary semimajor axis and eccentricity evolution that reproduces very well the mean behavior of thefull tidal equations and provides a simple criterion to determine the migration directions of the circumbinary planets. This criterionpredicts that some of the confirmed circumbinary planets are tidally migrating inward, but others are migrating outward. However, thetypical timescales are predicted to be very long, and not much orbital tidal evolution is expected to have taken place in these systems.Finally, we revisit the orbital evolution of a circumbinary planet in the framework of the constant time lag model. We find that theresults predicted with this formalism are identical to those obtained with creep theory in the limit of gaseous bodies