Metric for two arbitrary Kerr sources

The full metric describing a stationary axisymmetric system of two arbitrary Kerr sources, black holes or hyperextreme objects, located on the symmetry axis and kept apart in equilibrium by a massless strut is presented in a concise explicit form involving five physical parameters. The binary system composed of a Schwarzschild black hole and a Kerr source is a special limiting case of the general formulas, and we elaborate the metric for this physically interesting configuration too. (C) 2019 The Authors. Published by Elsevier B.V.