Gravitational redshift in Kerr-Newman geometry

Abstract

It is well known fact that gravitational mass can alter the space time structure and gravitational redshift is one of its examples. Static electric or magnetic charge can also alter the space time structure, similar to gravitational mass, giving rise to its effect on redshift. This can also be considered as electro and magneto static redshift. Gravitational redshift has been reported by most of the authors without consideration of static electric and / or magnetic charges present in the rotating body. In the present paper, we considered the three parameters: mass, rotation parameter and charge to discuss their combined effect on redshift, for a charged rotating body by using Kerr - Newman metric. It has been found that, the presence of electrostatic and magnetostatic charge increases the value of so-called gravitational redshift. Calculations have been also done here to determine the effect of electrostatic and magnetostatic charges on the amount of redshift of a light ray emitted at various latitudes from a charged rotating body. The variation of gravitational redshift from equatorial to non- equatorial region has been calculated, for a given set of values of electrostatic and magnetostatic charges.