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 |v _ { kick } | and the final black-hole spin a _ { fin } in terms of the dimensionless spins a _ { 1 } and a _ { 2 } of the two initial black holes .
Overall they suggest a maximum recoil velocity of |v _ { kick } | = 441.94 { km / s } , and minimum and maximum final spins a _ { fin } = 0.3471 and a _ { fin } = 0.9591 , respectively .