Many giant exoplanets are found near their Roche limit and in mildly eccentric orbits. This suggests that whenever a planet
crosses the Roche limit, it is not quickly disintegrated but might be only partially consumed,
leaving behind lower-mass planets.
Different outcomes of RLOF at periastron for different initial conditions and star radii. The orbits of the
planet, the star, and the particle are depicted in the (x–y) plane, where x and y are normalized to the initial periastron distance. The location of the Lagrangian point at
periastron is depicted with a black star while connecting lines show the relative distance of planet–particle (red) and star–particle (yellow) in different phases
along the orbit. Left panel: no impact; it is possible that a disk is formed (DISK). Middle panel: direct impact (DI) on stellar surface due to the presence of a larger star.
Right panel: the lost particle undergoes self-accretion (SA) due to the more eccentric orbit.
Color-shaded regions depict the parameter space for which
either DI or DISK occurs. Outside these areas, SA takes over. A darker tone of
red refers to larger initial eccentricity, which restricts the DI/DISK regime. DI/
DISK dominates at low eccentricities, while for eccentricities higher than 0.2,
the only possible outcome is SA. The black region refers to the highest
eccentricity that allows for DISK/DI.
Here we consider low-eccentricity systems, e < 0.2, and set the mass of the star to one solar mass. Color-shaded regions separate the “DISK” regime (a disk always
forms regardless of the initial rotation and eccentricity) from the “DI or DISK” regime (DISK or DI
depending on the initial set-up ). The black line refers to maximum allowed star radius, i.e., in the white area
the planet and the star are in contact. At low eccentricities RLOF at periastron
leads to DISK formation for most systems.
