Effects of Magnetic Charge on Orbital Dynamics in Einstein–Bronnikov Regular Black Holes

Abstract This work investigates the influence of the magnetic charge parameter q m on the orbital dynamics of test particles in Einstein–Bronnikov (EB) regular black holes. Employing a second post-Newtonian (2PN) approximation, we derive analytical solutions for orbital energy, angular momentum, and quasi-Keplerian motion, focusing on how q m modulates key observables such as orbital periods and periastron advance. Theoretical modeling reveals that q m significantly suppresses periastron advance at the first post-Newtonian order through nonlinear electrodynamics–induced nonlinear electromagnetic repulsion, while inducing a nonlinear contraction of orbital periods at the 2PN order, thereby validating the parameter’s order-dependent dynamical effects and distinguishing EB black holes from Reissner–Nordström counterparts. By applying observational data from the S2 star’s orbital precession around Sgr A*, we give a preliminary and qualitative constraint for the magnetic charge. This establishes a novel discriminative framework for probing regular black hole geometries against classical gravitational theories through combined orbital dynamics and horizon structure analysis.