Origin of the GJ 1148 Planetary System by Planet-Planet Scattering

Abstract

<p>The GJ 1148 system has two Saturn-mass planets orbiting around an M dwarf star on eccentric orbits (e = 0.375 for both planets), with orbital periods of 41.4 and 532 days. The inner planet is in the regime of eccentric warm Jupiters. We have performed numerical experiments to study the planet-planet scattering scenario for the origin of this orbital architecture. We consider a third planet of 0.1 or 0.227 M_J (Jupiter’s mass) in the initial GJ 1148 system with initial orbital separations of 3.5, 4, and 4.5 mutual Hill radii. The majority of scattering results in planet-planet collisions, followed by planet ejections, and the removal of planets that come too close to the star. Among them, only the post-ejection two-planet systems have similar properties to the GJ 1148 system. Therefore, the simulation results suggest that the GJ 1148 system may have lost a giant planet. We have also performed simulations of the general problem of the origin of warm Jupiters by planet-planet scattering. As in the GJ 1148 simulations, a non-trivial number of stable two-planet systems are produced by ejection, which disagrees with the result from another study showing that two-planet systems arise exclusively through planet-planet collisions.<br></p>