Binary system of unequal counterrotating Kerr-Newman sources

TL;DR

This paper derives an exact 6-parameter solution for a binary system of unequal counterrotating Kerr-Newman black holes, analyzing their horizon properties and singularity structure.

Contribution

It provides a new explicit analytical form for the horizon parameters and full metric of interacting Kerr-Newman black holes with unequal rotation.

Findings

Explicit horizon parameter expressions in terms of physical quantities

Conditions for absence of naked singularities off the axis

Closed-form metric for extreme black hole configurations

Abstract

Stationary axisymmetric binary systems of unequal counterrotating Kerr-Newman sources with a massless strut in between are studied. By means of the choice of a suitable parametrization, the axis conditions and the absence of individual magnetic charges are fulfilled; thus, the entire metric reduces to a 6-parametric asymptotically flat exact solution. Later on, with the purpose to describe interacting black holes, the analytic functional form of the horizon half-length parameter $\sigma_{k}$ is obtained explicitly in terms of physical Komar parameters: mass $M_{k}$, electric charge $Q_{k}$, angular momentum $J_{k}$, and coordinate distance $R$, where the seven physical parameters satisfy a simple algebraic relation. Finally, in the limit of extreme black holes, the full metric is derived in a closed analytical form, and a study on the absence or appearance of naked singularities off the axis is presented.