Dynamical evolution of a young planetary system: stellar flybys in co-planar orbital configuration

Abstract: Stellar flybys in star clusters may perturb the evolution of young planetary systems in terms of disk truncation, planetary migration and planetary mass accretion. We investigate the feedback of a young planetary system during a single close stellar encounter in a typical open young stellar cluster. We consider 5 masses for the stellar perturbers: 0.5, 0.8, 1, 3 and 8 M$_{Sun}$, in coplanar, prograde and retrograde orbits respect to the planetary disk, varying the pertruber-host star orbital periastron from 100 AU to 500 AU. We have made 3D modelizations with the smooth particle hydrodynamics code GaSPH of a system composed by a solar type star surrounded by a low density disk where a giant planet is embedded in. We focus on the dynamical evolution of global parameters characterizing the disk and the planet, like the Lagrangian radius containing the $63.2\%$ of the mass of the disk, the distance of the planet to its host star, the planet orbital eccentricity and the planetary mass accretion. We find that the most part of the simulated systems show a significant disk truncation after a single close encounter, a final orbital distance of the Jovian, from the central star, lower than the unperturbed case and, finally, the perturbed systems show a final mass accretion of the Jovian planet larger than the non-perturbed case. Therefore, stellar flybys significantly perturb the dynamics of a young planetary system, regardless the orbital configuration of the stellar perturber. In such experiments, the final disk radius and the orbital parameters of the Jovian planet are considerably affected by the stellar close encounter.