QPOs from charged particles around charged black holes in STVG

Abstract This study investigates the dynamics of electrically charged test particles around electrically charged Reissner–Nordström (RN) black holes (BHs) in scalar-tensor-vector gravity (STVG), known as modified gravity (MOG). Using Lagrangian and Hamiltonian formalisms, we derive the effective potential governing the motion of charged particles, taking into account interactions between the electrostatic field and the MOG field, and determine the innermost stable circular orbit (ISCO). The results indicate that an increase in the MOG parameter leads to shifting out the position of ISCOs, thereby altering the orbital dynamics of test particles compared to those predicted by general relativity (GR). We also study the radiation properties of the black hole accretion disc, including radiation flux, temperature distribution within the disc, and total radiation luminosity. We derive Keplerian and oscillation frequencies of charged particles around the charged MOG BH together with applications to quasi-periodic oscillations (QPOs) in the frame of relativistic precession (RP) model. The analysis incorporates the Markov Chain Monte Carlo (MCMC) statistical method to compare BH parameters with observed quasi-periodic oscillations (QPOs) data. The MCMC modeling results show a strong agreement with QPO observations from microquasars (GRO J1655−40, XTE J1550−564), intermediate-mass BHs (M82 X-1), and the supermassive BH Sgr A* at the Galactic center. This study confirms the astrophysical relevance of MOG theories and emphasizes the importance of further investigations into the effects of strong magnetic fields around BHs.