Superposed metric for spinning black hole binaries approaching merger

Accurately describing binary spinning black hole mergers is challenging and computationally expensive. In this paper, Combi et al. provide a semianalytic approach to the problem of a spin-aligned binary in the inspiral phase by proposing an approximate solution of general relativity in the form of a linear superposition of boosted Kerr metrics. They demonstrate that it provides an accurate basis for general relativistic magnetohydrodynamic simulations of accreting mini-disks around the black holes.