  The discovery of many giant planets in close-in orbits and the effect of
planetary and stellar tides in their subsequent orbital decay have been
extensively studied in the context of planetary formation and evolution
theories. Planets orbiting close to their host stars undergo close encounters,
atmospheric photoevaporation, orbital evolution, and tidal interactions. In
many of these theoretical studies, it is assumed that the interior properties
of gas giants remain static during orbital evolution. Here we present a model
that allows for changes in the planetary radius as well as variations in the
planetary and stellar dissipation parameters, caused by the planet's
contraction and change of rotational rates from the strong tidal fields. In
this semi-analytical model, giant planets experience a much slower
tidal-induced circularization compared to models that do not consider these
instantaneous changes. We predict that the eccentricity damping time-scale
increases about an order of magnitude in the most extreme case for too inflated
planets, large eccentricities, and when the planet's tidal properties are
calculated according to its interior structural composition. This finding
potentially has significant implications on interpreting the
period-eccentricity distribution of known giant planets as it may naturally
explain the large number of non-circularized, close period currently known.
Additionally, this work may help to constrain some models of planetary
interiors, and contribute to a better insight about how tides affect the
orbital evolution of extrasolar systems.

Earth and Planetary Astrophysics