QPOs tests and circular motions of charged particles around magnetized Bocharova–Bronnikov–Melnikov–Bekenstein black holes

Abstract Testing gravity theories beyond General Relativity (GR) is crucial for a deeper understanding of fundamental physics, especially in the strong gravitational field regime around astrophysical compact objects. This work examines quasi-periodic oscillations (QPOs) generated by charged particles orbiting magnetized Bocharova–Bronnikov–Melnikov–Bekenstein (BBMB) black holes. We study charged particles’ circular orbits, deriving expressions for energy and angular momentum influenced by scalar and magnetic interactions, and investigate the innermost stable circular orbit (ISCO). Using the relativistic precession (RP) model, we derive the fundamental orbital, radial, and vertical frequencies of charged particle oscillations, highlighting deviations caused by conformal scalar and magnetic interactions. Our analysis shows that the conformally coupled scalar field significantly modifies the spacetime curvature, producing a repulsive gravitational effect that shifts stable orbits outward, thereby reducing the radial oscillation frequency. Using observational QPO data from well-known astrophysical sources-GRS 1915+105, GRO J1655-40, M82 X-1, and Sgr A*-we performed Markov Chain Monte Carlo (MCMC) simulations to constrain black hole mass, scalar coupling, magnetic interaction, and orbital radius parameters. Our results reveal significant deviations from standard General Relativity predictions, offering clear evidence of scalar and magnetic field influences. These findings indicate that scalar and magnetic fields produce observable shifts in QPO frequencies, providing promising observational signatures to test alternative gravitational theories in extreme astrophysical environments.