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| We present a summary of our recent investigations on the evolutions of orbit and mass ratio of a gas-accreting planet pair. The main aim of this study is to explain the mass configurations of the exoplanet pairs that are in compact orbital configurations(i.e. in or near the mean motion resonances(MMRs)). We assume the two planet cores had already reached the critical masses($15 or 30$ Earth masses), so that we only focus on the runaway gas accretion phase. To be consistent, We begin with the cases with single planet core embedded in various disks. The results show that large planet core usually results in small gas planet and dominant factor of the final planet mass is the viscosity of the disk. Our further simulations with two planet cores show that, if the two cores accrete gas simultaneously, they will undergo convergent migration and eventually be trapped in the $2:1$ MMR. Furthermore, their mass ratio changes during the migration and the final mass of the outer planet is always more massive than or equal to that of the inner one. |
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| Keywords:celestial mechanics, gas giant, proto-stellar disk, mean motion resonance |
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