Radiation from an emitter revolving around a magnetized nonrotating black hole

One of the methods of study of black holes in astrophysics is based on broadening of the spectrum of radiation of ionized iron atoms. The line K alpha associated with iron emission at 6.4 keV is very narrow. If such an ion is revolving around a black hole, this line is effectively broadened as a result of the Doppler and gravitational redshift effects. The profile of the broadened spectrum contains information about the gravitational field of the black hole. In the presence of a regular magnetic field in the vicinity of a black hole, the characteristics of the motion of charged ions are modified. In particular, their innermost stable circular orbits become closer to the horizon. The purpose of this work is to study how this effect modifies the spectrum broadening of lines emitted by such an ion. Our final goal is to analyze whether the change of the spectrum profiles can give us information about the magnetic field in the black hole vicinity.