Physics
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufm.p31a1380l&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #P31A-1380
Physics
5205 Formation Of Stars And Planets, 5455 Origin And Evolution, 5744 Orbital And Rotational Dynamics (1221), 5749 Origin And Evolution, 6296 Extra-Solar Planets
Scientific paper
We have analyzed the orbital and mass evolution of planets that undergo run-away gas accretion in a circumstellar disk by means of high-resolution, three-dimensional hydrodynamics simulations. The radial distribution of the disk torque per unit disk mass provides an important diagnostic for the nature of the disk-planet interactions. We first show that torque distributions for nonmigrating planets of fixed mass are in general agreement with the expectations of resonance theory. We then present results of calculations for migrating, mass-gaining planets. Our main findings are: (1) For planets with an initial mass Mp=5 Earth masses, which are embedded in disks with standard parameters (aspect ratio h~ 0.04--0.05 and alpha-viscosity ~ 0.001--0.1) and which undergo run-away gas accretion growth to one Jupiter mass, the torque distributions per unit disk mass are largely unaffected by migration and accretion for a given planet mass. The migration rates of these planets are in agreement with the predictions of the standard theory for planet migration (Type I and Type II migration). In the intermediate and Jupiter-mass regimes, migration rates can be accounted for by standard Type I theory, corrected for the gas depletion in the gap region. (2) The planet mass growth rate is dMp/dt∝ M3p/h7 (gas capture within the planet's Bondi sphere) at lower planet masses and dMp/dt∝ Mp/h (gas capture within the planet's Hill sphere) at intermediate planet masses. At higher planet masses, the accretion rate reduces due to gap formation. (3) During the run-away mass growth phase, a planet migrates inwards by only about 20% in radius before achieving a mass on the order of Jupiter's. (4) For standard planet and disk conditions, we find no evidence of fast migration driven by coorbital torques (Type III migration). We do find evidence of Type III migration for a planet of fixed Saturn's mass, which is immersed in a cold (h~ 0.03) and massive (~ 0.02 M&sun;) disk, whose migration begins before gap formation completes. The migration can be explained with a model in which the torque is due to an asymmetry in density between trapped gas on the leading side of the planet and ambient gas on the trailing side of the planet.
D'Angelo Gennaro
Lubow Stephen H.
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