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Abstract

Binary black hole systems with spins aligned with the orbital angular momentum are of special interest, as they may be the preferred end state of the inspiral of generic supermassive binary black hole systems. In view of this, we have computed the inspiral and merger of a large set of binary systems of equal-mass black holes with spins aligned with the orbital angular momentum but otherwise arbitrary. By least-square fitting the results of these simulations, we have constructed two “spin diagrams” which provide straightforward information about the recoil velocity and the final black hole spin in terms of the dimensionless spins and of the two initial black holes. Overall, they suggest a maximum recoil velocity of km s−1, and minimum and maximum final spins and , respectively.