Supermassive Recoil Velocities for Binary Black-Hole Mergers with Antialigned Spins

Recent calculations of the recoil velocity in binary black-hole mergers have found the kick velocity to be of the order of a few hundred km/s in the case of nonspinning binaries and about 500  km/s in the case of spinning configurations, and have lead to predictions of a maximum kick of up to 1300  km/s. We test these predictions and demonstrate that kick velocities of at least 2500  km/s are possible for equal-mass binaries with antialigned spins in the orbital plane. Kicks of that magnitude are likely to have significant repercussions for models of black-hole formation, the population of intergalactic black holes, and the structure of host galaxies.