EVOLVING THE BOWEN-YORK INITIAL DATA FOR SPINNING BLACK-HOLES

The Bowen-York initial value data typically used in numerical relativi ty to represent a spinning black hole are not those of a constant-time slice of the Kerr spacetime. If Bowen-York initial data are used for each black hole in a collision, the emitted radiation will be partiall y due to the ''relaxation'' of the individual holes to Kerr form. We c ompute this radiation by treating the geometry for a single hole as a perturbation of a Schwarzschild black hole, and by using second order perturbation theory. We discuss the extent to which Bowen-York data ca n be expected accurately to represent Kerr holes.