Explorations into the Viability of Coupled Radius-Orbit Evolutionary Models for Inflated Planets - Astrophysics > Earth and Planetary AstrophysicsReport as inadecuate




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Abstract: The radii of some transiting extrasolar giant planets are larger than wouldbe expected by the standard theory. We address this puzzle with the model ofcoupled radius-orbit tidal evolution developed by\citet{Ibgui and Burrows 2009}. The planetary radius is evolvedself-consistently with orbital parameters, under the influence of tidal torquesand tidal dissipation in the interior of the planet. A general feature of thismodel, which we have previously demonstrated in the generic case, is that apossible transient inflation of the planetary radius can temporarily interruptits standard monotonic shrinking and can lead to the inflated radii that weobserve. In particular, a bloated planet with even a circular orbit may stillbe inflated due to an earlier episode of tidal heating. We have modified ourmodel to include an orbital period dependence of the tidal dissipation factorin the star, $Q- {\ast} \propto P^{\gamma}$, $-1 \leqslant \gamma \leqslant 1$.With this model, we search, for a tidally heated planet, orbital and radiusevolutionary tracks that fall within the observational limits of the radius,the semimajor axis, and the eccentricity of the planet in its current estimatedage range. We find that, for some inflated planets WASP-6b and WASP-15b,there are such tracks; for another TrES-4, there are none; and for stillothers WASP-4b and WASP-12b, there are such tracks, but our model might implythat we are observing the planets at a special time. Finally, we stress thatthere is a two to three order-of-magnitude timescale uncertainty of theinspiraling phase of the planet into its host star, arising from uncertaintiesin the tidal dissipation factor in the star $Q- {\ast}$.



Author: Laurent Ibgui, David S. Spiegel, Adam Burrows

Source: https://arxiv.org/







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