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arXiv · 1401.4457

Scattering outcomes of close-in planets: constraints on planet migration

Cristobal Petrovich·Scott Tremaine·Roman R. Rafikov
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Abstract

Many exoplanets in close-in orbits are observed to have relatively high eccentricities and large stellar obliquities. We explore the possibility that these result from planet-planet scattering by studying the dynamical outcomes from a large number of orbit integrations in systems with two and three gas-giant planets in close-in orbits (0.05 AU < a < 0.15 AU). We find that at these orbital separations, unstable systems starting with low eccentricities and mutual inclinations ($e\lesssim0.1$, $i\lesssim0.1$) generally lead to planet-planet collisions in which the collision product is a planet on a low-eccentricity, low-inclination orbit. This result is inconsistent with the observations. We conclude that eccentricity and inclination excitation from planet-planet scattering must precede migration of planets into short-period orbits. This result constrains theories of planet migration: the semi-major axis must shrink by 1-2 orders of magnitude without damping the eccentricity and inclination.

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Cristobal Petrovich, Scott Tremaine, Roman R. Rafikov. 2014-01-17. Scattering outcomes of close-in planets: constraints on planet migration. https://doi.org/10.1088/0004-637x/786/2/101

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