Estimating the Parameters of the Hybrid Palatini Gravity Model with the Schwarzschild Precession of S2, S38 and S55 Stars: Case of Bulk Mass Distribution

Abstract

We estimate the parameters of the Hybrid Palatini gravity model with the Schwarzschild precession of S-stars, specifically of the S2, S38 and S55 stars. We also take into account the case of bulk mass distribution near the Galactic Center. We assume that the Schwarzschild orbital precession of mentioned S-stars is the same as in General Relativity (GR) in all studied cases. In 2020, the GRAVITY Collaboration detected the orbital precession of the S2 star around the supermassive black hole (SMBH) at the Galactic Center and showed that it is close to the GR prediction. The astronomical data analysis of S38 and S55 orbits showed that, also in these cases, the orbital precession is close to the GR prediction. Based on this observational fact, we evaluated the parameters of the Hybrid Palatini Gravity model with the Schwarzschild precession of the S2, S38 and S55 stars, and we estimated the range of parameters of the Hybrid Palatini gravity model for which the orbital precession is as in GR for all three stars. We also evaluated the parameters of the Hybrid Palatini Gravity model in the case of different values of bulk mass density distribution of extended matter. We believe that proposed method is a useful tool to evaluate parameters of the gravitational potential at the Galactic Center.

Keywords

• alternative theories of gravity
• supermassive black hole
• stellar dynamics