Circular orbits of test particles interacting with massless linear scalar field of the naked singularity

We study effects of the particles coupling with scalar field (SF) on the distribution of stable circular orbits (SCO) around the naked singularity described by the well-known Fisher-Janis-Newman-Winicour solution (F/JNW). The power-law and exponential models of the particle–SF interaction are analyzed. The focus is on the nonconnected SCO distributions. A method is used that facilitates numerical studies of the SCO regions in the case of the general static spherically symmetric metric. In case of F/JNW, we show that coupling between particles and SF can essentially complicate the topology of the SCO distributions. In particular, it can lead to new nonoverlapping SCO regions, which are separated by unstable orbits and/or by regions where the circular orbits do not exist.