Metric for two equal Kerr black holes

We show that the exact solution of Einstein’s equations describing a binary system of aligned identical Kerr black holes separated by a massless strut follows straightforwardly from the extended 2-soliton solution possessing equatorial symmetry. We give its concise analytic form in terms of physical parameters and then compare with our old solution of that problem obtained in canonical parametrization, demonstrating the equivalence of the two approaches. A surprising physical by-product of our analysis is the discovery that up to three different configurations of two corotating Kerr sources can have equal masses and equal angular momenta. We also introduce physical parametrization to the general six-parameter asymmetric configuration which permits to treat analytically the case of two nonequal corotating black holes.