Extra-large remnant recoil velocities and spins from near-extremal-Bowen-York-spin black-hole binaries

Abstract

We evolve equal-mass, equal-spin black-hole binaries with specific spins of a/mH ∼ 0.925, the highest spins simulated thus far and nearly the largest possible for Bowen-York black holes, in a set of configurations with the spins counter-aligned and pointing in the orbital plane, which maximizes the recoil velocities of the merger remnant, as well as a configuration where the two spins point in the same direction as the orbital angular momentum, which maximizes the orbital hang-up effect and remnant spin. The coordinate radii of the individual apparent horizons in these cases are very small and the simulations require very high central resolutions (h ∼ M/320). We find that these highly spinning holes reach a maximum recoil velocity of ∼ 3300 km s −1 (the largest simulated so far) and, for the hangup configuration, a remnant spin of a/mH ∼ 0.922. These results are consistent with our previous predictions for the maximum recoil velocity of ∼ 4000 km s −1 and remnant spin; the latter reinforcing the prediction that cosmic censorship is not violated by merging highlyspinning black-hole binaries. We also numerically solve the initial data for, and evolve, a single maximal-Bowen-York-spin black hole, and confirm that the 3-metric has an O(r −2 ) singularity at the puncture, rather than the usual O(r −4 ) singularity seen for non-maximal spins.

Gravitational recoil from accretion-aligned black-hole binaries

“…Note here that the orientation ϕ is the angle that the spin of BH1 (the BH originally located on the positive x axis) makes with the spin of BH1 in the corresponding AsTHxxxPH0 configuration in a rotated frame where infall directions all coincide (see [46]). Also note that the largest measured recoil for these runs is (4079.5 ± 10.1) km s −1 for the A9TH60PH30 and A9TH60PH210 configurations, which exceeds both the largest measured quasicircular "superkick recoil" of 3300 km s −1 [47] and even the theoretical "superkick maximum" recoil of 3680 ± 130 km s −1 [40]. The values given for the spins near merger should only be taken as an approximation.…”

Can binary mergers produce maximally spinning black holes?

“…Equal-mass BBH mergers might lead to higher final spins than expected, rivaling the highest spins (χ ≃ 0.998) allowed by physical accretion flows [20]. Black holes can always be spun up by Square points are simulations from [16]; the purple X is from [17]. Bottom panel: The final spin parameter χ f (ν) for these mergers.…”

Superkicks in Hyperbolic Encounters of Binary Black Holes

“…One remarkable discovery has been kicks of a few thousand km s −1 found in configurations of equal-mass binaries with initially anti-aligned spins in the orbital plane [14,15,16]. For near extremal spins (a/m = 0.925), recoils as large as 3, 300 km s −1 have been computed [17].Motivated by our previous study [18] of the final spin of BHs from scattering mergers of BBHs, we present the first extension of gravitational recoil to hyperbolic encounters. There are crucial differences between hyperbolic and quasi-circular configurations that affect the kick to the final BH.…”