Scattering of massive particles from black holes and naked singularities

ABSTRACT We performed a numerical study of the dynamics of massive particles orbiting black holes and naked singularities in the Reissner–Nordström geometry. We modelled a stream of particles with a constant angular momentum and with a range of energies. We then solved the geodesic equation of motion and compared the trajectories around black holes and naked singularities by tuning the charge parameter of the metric. The set-up allows us to explore the orbital dynamics relevant for astrophysical scenarios such as tidal disruption events, particularly for deep encounters. We discussed differences and similarities in the orbital dynamics and deflection angles. We found that particles reflected by a black hole follow a stream-like family of orbits within a narrow range of deflection angles, whereas in the case of naked singularities particles are scattered in all directions on the plane of motion. We explained this behaviour as an interplay between the presence of a centrifugal barrier at the location of the unstable circular orbit and an absorbing event horizon in the case of a black hole or a repulsive core in the case of a naked singularity. These qualitative differences are expected to impact the observable signatures of tidal disruption events.