The antikick strikes back: recoil velocities for nearly-extremal binary black hole mergers in the test-mass limit

Understand

Gravitational waves emitted from a generic binary black-hole merger carry away linear momentum anisotropically, resulting in a gravitational recoil, or "kick", of the center of mass.

• For certain merger configurations the time evolution of the magnitude of the kick velocity has a local maximum followed by a sudden drop.
• Perturbative studies of this "antikick" in a limited range of black hole spins have found that the antikick decreases for retrograde orbits as a function of negative spin.
• We analyze this problem using a recently developed code to evolve gravitational perturbations from a point-particle in Kerr spacetime driven by an effective-one-body resummed radiation reaction force at linear order in the mass ratio $\nu\ll 1$.