Charged Particles Circular Orbits around Weakly Charged and Magnetized Kerr Black Holes

We study the circular orbits of charged particles around a weakly charged Kerr black hole immersed in a weak, axisymmetric magnetic field. Firstly, we review the circular orbits of neutral particles. We then review the circular orbits of charged particles around a weakly charged Kerr black hole and weakly magnetized Kerr black hole. The case of a weakly magnetized and charged black hole is investigated thereafter. We investigate, in particular, the effect of the electromagnetic forces on the charged particles' innermost stable circular orbits. We examine the conditions for the existence of negative-energy stable circular orbits and the possibility of the emergence of a gap or double orbit in thin accretion disks. Some of the interesting astrophysical consequences of our findings are discussed as well.Comment: Accepted for publication in the Astrophysical Journal. arXiv admin note: substantial text overlap with arXiv:2208.1395

Tilted Circular Orbits around a Kerr Black Hole

We study circular orbits that are tilted with respect to the equatorial plane around a Kerr black hole. We write the equations for the parameters of a tilted circular orbit in terms of the orbit's radius and the Carter constant, or equivalently, the tilt angle. The tilted innermost stable circular orbits (TISCO)s are discussed as well as the last circular orbits. The azimuthal precession of an orbit is then studied and an approximate expression for the precession speed is given. We finally try to link tilted circular orbits to quai-periodic oscillations in some astrophysical black hole systems.Comment: This paper had been accepted for publication in PR