On the Origin of the Eccentricities of Extrasolar Planets

Abstract

We develop a phenomenological theory that aims to account for the origin of the large eccentricities of extrasolar planets and that of the small eccentricities in the solar system, the preference for apsidal alignment in non-resonant multiplanet systems, and the origin of the similarities in the eccentricity distribution of extra-solar planets and that of spectroscopic binary stars. We show that if a physical process is weakly dependent on the local dynamics of the companion and imparts a small relative acceleration to the star-companion system, the eccentricity of the companion's orbit is excited to large values depending on the direction and duration of acceleration. A natural candidate for such processes are asymmetric stellar jets and star-disk winds. When the acceleration originates from a precessing jet, large eccentricities can be excited by the resonance of the jet's precession frequency with the induced acceleration's excitation frequency even for nearly perpendicular jets. Precession also reduces the eccentricity amplitude far inside the resonance radius. The acceleration's strength is best constrained in multiplanet systems because of the companions' mutual gravitational perturbations, while the acceleration's duration is bounded by the condition that the residual velocity imparted to the star is smaller than the stellar velocity dispersion in the Galaxy. In the outer parts of the star-companion system where the acceleration excitation time is comparable to or smaller than the orbital period, significant radial migration takes place which may have important consequences for the dynamics of the minor body populations in the solar system. The theory is illustrated with the $\upsilon$ Andromedae binary system.

41 pages, 14 figures, accepted for publication in the Astronomical Journal

References in corpus (3)

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• Scenarios for the Origin of the Orbits of the Trans-Neptunian Objects 2000 CR105 and 2003 VB12
• Excitation and Propagation of Eccentricity Disturbances in Planetary Systems

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