Zoom-Whirl Behavior and Near-Extremal Black Holes in Relativistic Mergers of Charged Black Hole Binaries

It has previously been demonstrated [1] that near-extremal black holes with dimensionless spin parameter j ≥ 0.95 can be produced by the merger of two highly-boosted, non-rotating, uncharged, equal-mass black holes. The same study also showed that zoom-whirl orbits can be exhibited by the binaries prior to merger, dependent on the impact parameter and initial separation. We extend this investigation to black holes with electric charge, conducting simulations of relativistic mergers of equal-mass, non-rotating, equal-charge binary black holes. We investigate the effects of impact parameter and charge-to-mass ratio on the extremality of the merger remnant and zoom-whirl behavior. We find merger remnants with Kerr-Newman extremality parameters that exceed 0.95. [1] Sperhake, U. et al. Phys. Rev. Lett. 103, 131102 (2009).