Periodic equatorial orbits in a black bounce scenario

Abstract

We study equatorial closed orbits in a popular black bounce model to see if the internal structure of these objects could lead to peculiar observable features. Paralleling the analysis of the Schwarzschild and Kerr metrics, we show that in the black bounce case each orbit can also be associated with a triplet of integers which can then be used to construct a rational number characterizing each periodic orbit. When the black bounce solution represents a traversable wormhole, we show that the previous classification scheme is still applicable with minor adaptations. We confirm in this way that this established framework enables a complete description of the equatorial dynamics across a spectrum of cases, from regular black holes to wormholes. Varying the black bounce parameter rmin, we compare the trajectories in the Simpson-Visser model with those in the Schwarzschild metric (and the rotating case with Kerr). We find that in some cases even small increments in rmin can lead to significant changes in the orbits.