Probing a black-bounce-Reissner-Nordstrom spacetime with precessing and periodic motion

We investigate the precessing and periodic orbits of a test timelike particle around the black-bounce-Reissner-Nordstrom spacetime which is characterized by its charge and bounce parameter. Its marginally bound orbit and innermost stable circular orbit are obtained in the exact forms. We pay closely attention to its precessing orbits and find the resulting relativistic periastron advance. We also study its periodic orbits and demonstrate that small variations of the charge and bounce parameter can make the motion jump among the periodic and precessing orbits. In these two kinds of orbits, we find a distinct degeneracy that some specific combinations of the charge and bounce parameters can generate exactly the same orbital motion in the black-bounce-Reissner-Nordstrom spacetime, which can also mimic those of the Schwarzschild black hole. In order to break such a degeneracy, we make use of the precession of S2 star around Sgr A* detected by GRAVITY together with the shadow diameter of Sgr A* measured by Event Horizon Telescope and find preliminary bounds on the charge and bounce parameter.

Automated summary

The precessing and periodic orbits of a test timelike particle around the black-bounce-Reissner-Nordstrom spacetime, characterized by its charge and bounce parameter, are investigated. The exact forms of its marginally bound orbit and innermost stable circular orbit are obtained. Attention is given to the precessing orbits and the resulting relativistic periastron advance is found. The study also looks at the periodic orbits and shows that small variations in the charge and bounce parameter can cause the motion to switch between periodic and precessing orbits. A distinct degeneracy is found in these two types of orbits, where specific combinations of the charge and bounce parameters can generate the exact same orbital motion in the black-bounce-Reissner-Nordstrom spacetime, mimicking that of the Schwarzschild black hole. To break this degeneracy, GRAVITY's observation of the precession of S2 star around Sgr A* and the shadow diameter measurements of Sgr A* by the Event Horizon Telescope are used to provide preliminary bounds on the charge and bounce parameter.