Evolution of Giant Planets in Eccentric Disks

We investigate the interaction between a giant planet and a viscouscircumstellar disk by means of high-resolution, two-dimensional hydrodynamicalsimulations. We consider planet masses that range from 1 to 3 Jupiter masses(Mjup) and initial orbital eccentricities that range from 0 to 0.4. We findthat a planet can cause eccentricity growth in a disk region adjacent to theplanet's orbit, even if the planet's orbit is circular. Disk-planetinteractions lead to growth in a planet's orbital eccentricity. The orbitaleccentricities of a 2 Mjup and a 3 Mjup planet increase from 0 to 0.11 withinabout 3000 orbits. Over a similar time period, the orbital eccentricity of a 1Mjup planet grows from 0 to 0.02. For a case of a 1 Mjup planet with an initialeccentricity of 0.01, the orbital eccentricity grows to 0.09 over 4000 orbits.Radial migration is directed inwards, but slows considerably as a planet'sorbit becomes eccentric. If a planet's orbital eccentricity becomessufficiently large, e > ~0.2, migration can reverse and so be directedoutwards. The accretion rate towards a planet depends on both the disk and theplanet orbital eccentricity and is pulsed over the orbital period. Planet massgrowth rates increase with planet orbital eccentricity. For e~0.2 the massgrowth rate of a planet increases by approximately 30% above the value for e=0.For e > ~0.1, most of the accretion within the planet's Roche lobe occurs whenthe planet is near the apocenter. Similar accretion modulation occurs for flowat the inner disk boundary which represents accretion toward the star.Comment: 20 pages 16 figures, 3 tables. To appear in The Astrophysical Journal vol.652 (December 1, 2006 issue