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This paper is devoted to the analysis of the dynamics of test particles in the vicinity of a black hole within the framework of a gravitational aether model. First, we explored the structure of spacetime by analyzing the curvature scalars. Then, we studied particle dynamics around a black hole using the Hamilton–Jacobi equation.The influence of the aether on the effective potential of the radial motion of test particles around the black hole has been investigated. The dependence of the innermost stable circular orbits (ISCO) on the aether parameter has also been investigated. We also considered particle collision near the black hole in the presence of aether, and studied the fundamental frequencies of the orbital motion of the test particles around the black hole in the presence of aether. Further, we applied the obtained results to the analysis of the upper and lower frequencies of twin-peaked quasiperiodic oscillations (QPOs) occurring near black holes. Finally, we use theoretical and numerical results to obtain constraints on model parameters using observation data in QPO. [ABSTRACT FROM AUTHOR]

We investigate the dynamics of test particles endowed with both electric charge and a magnetic dipole moment around a Schwarzschild black hole (BH) immersed in an externally asymptotically uniform magnetic field. We further analyse the effective potential and specific angular momentum and energy of the particles. Furthermore, we show that the upper limit for magnetic interaction parameter β increases with increasing cyclotron frequency ω B , while the radius of the innermost stable circular orbit (ISCO) for charged test particles decreases for the upper value of β = β upper . Furthermore, we show that the energy efficiency released from the BH increases up to about 90% due to the presence of the magnetic dipole moment of the test particle. We explore a degeneracy between the spin parameter of rotating Kerr BH and the magnetic parameter for the values of the ISCO radius and energy efficiency. We study in detail the centre of mass energy for collisions of charged and magnetized particles in the environment surrounding the Schwarzchild BH. Finally, as an astrophysical application, we explore the magnetized parameter and cyclotron frequency numerically for a rotating magnetized neutron star. Interestingly, we show that the corresponding values of the above-mentioned parameters for the magnetar PSR J1745-2900 that orbits around the supermassive black hole (SMBH) that exists at the centre of the Milky Way galaxy are ω B ≃ 5 and β ≃ 0.67 , respectively, for the magnetic field is about 10 G. [ABSTRACT FROM AUTHOR]

In this paper, we study the horizon properties and scalar invariants of the spacetime around a regular black hole (BH) in 4D Einstein Gauss-Bonnet (4D EGB) gravity. It is observed that the presence of both Gauss-Bonnet (GB) coupling and magnetic charge parameters causes the shrinking of the outer horizon. We find that the range of the GB parameter α / M 2 ∈ (− 0.15869 , 1) , and the extreme value of magnetic charge reaches up to g extr = 0.886 M , which allows for the existence of a BH horizon, while it is g extr = 0.7698 M for pure Bardeen BH. We also investigate the dynamics of magnetized particles around the magnetically charged Bardeen BH, assuming the particle's motion occurs in the equatorial plane in the proper observation frame, and the direction of the magnetic dipole moment of the particles is always kept radially and its magnitude is constant. Moreover, the dynamics of magnetically charged particles are also studied, and it is shown that both the energy and angular momentum of the particles corresponding to circular orbits increases with the increase of their magnetic charge. Finally, we also study collisions of magnetized, electrically neutral, and magnetically charged particles around the Bardeen BHs, where we provide analyses of critical angular momentum that may allow collision of the particles near-horizon radius, producing enormous values of center of mass energy of the collisions. [ABSTRACT FROM AUTHOR]