Displaced orbits and electric-magnetic black hole binaries

摘要

In presence of magnetic fields, the orbits of charged particles can be displaced from the equatorial plane. We study circular orbits of electrically charged massive objects around a magnetic black hole in the probe approximation. We show that there exist a one-parameter family of circular orbits at constant polar angle theta and constant radius r, parameterized by the angular momentum. The angle theta can be made arbitrarily small by increasing the charge-to-mass ratio of the orbiting particle, but when this is a Reissner-Nordstrom black hole, the condition q <= m implies that orbits exist only for vertical bar theta-pi/2 vertical bar