Gas Accretion Rate onto a Protoplanet during the Stage of Runaway Gas Accretion

Abstract

Interior models suggest that transiting giant extrasolar planets have a significant difference in the amount of heavy elements, including their solid cores. This divergence may have originated from planetesimals accreted onto a protoplanet during the stage of runaway gas accretion. Recent work suggests the rate of planetesimals accreted onto a protoplanet depends strongly on the rate of gas accretion. We have calculated the evolution of a protoplanet by using a one‐dimensional quasi‐static model and investigated gas accretion rates onto a protoplanet during runaway gas accretion. We have also examined the effects of changing the equation of state for gas, grain opacity, and an initial core mass on the results. After the onset of runaway gas accretion, the magnitude of gas accretion rates was strongly dependent on the three factors, but the dependence of gas accretion rates on planetary mass was not affected by them.