New treatment of red/blue shifts of emitted photons in terms of Kerr–Newman black hole parameters

Abstract

This study presents a method for determining the mass, angular momentum, and charge of Kerr–Newman black holes by analyzing the red/blue shifts of photons emitted by geodesic neutral massive objects. We derive the equations of motion for photons in the Kerr–Newman spacetime. We obtain explicit expressions for redshift/blueshift photons emitted by an object orbiting a Kerr–Newman black hole. Finally, using the Boyer–Lindquist coordinates, we express the red/blue shifts in terms of the metric parameters.