Princeton University Extrasolar Planet Discussion Group
Resonant Excitation of Planetary Eccentricity due to a Dispersing Eccentric Protoplanetary Disk: A New Mechanism of Generating Large Planetary Eccentricities
I will present a new mechanism of generating large planetary eccentricities. This mechanism applies to planets within the inner cavities of their companion protoplanetary disks. A massive disk with an inner truncation may become eccentric due to non-adiabatic effects associated with gas cooling, and can retain its eccentricity in long-lived coherently-precessing eccentric modes; as the disk disperses, the inner planet will encounter a secular resonance with the eccentric disk when the planet and the disk have the same apsidal precession rates; the eccentricity of the planet is then excited to a large value as the system goes through the resonance. In this talk, I will discuss how disks may spontaneously become eccentric through eccentric mode instability. Then, I will present an approximate secular dynamics model to calculate the long-term evolution of the "planet + dispersing eccentric disk" system. Our calculations find that the planet can attain a large eccentricity (between 0.1 and 0.6) in this model. This eccentricity excitation can be understood in terms of the mode conversion (``avoided crossing'') phenomenon associated with the evolution of the "planet + disk" eccentricity eigenstates.