On the relation of the mass, spin and charge parameters with the red and blue shiftsof photons emitted by particles orbiting a Kerr-Newman black hole

We found the mass M and rotation a parameters of the Kerr-Newman black hole in terms of the charge Q parameter as well as the red zr and blue zb shifts of light emitted by geodesic particles traveling in circular orbits around it for both cases: corotating and counterrotating directions. These shifts zr and zb cannot acquire arbitrary values; bounds of these shifts are found as functions of the parameters a and Q.