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.