COLLIDING BLACK-HOLES - HOW FAR CAN THE CLOSE APPROXIMATION GO

We study the head-on collision of two equal-mass momentarily stationar y black holes, using black hole perturbation theory up to second order . Compared to first-order results, this significantly improves agreeme nt with numerically computed wave forms and energy. Much more importan t, second-order corrections to provide ''error bars'' to the first-ord er results makes perturbation theory a viable tool for providing bench marks for numerical relativity in more generic collisions and, in some range of collision parameters, for supplying wave form templates for gravitational wave detection.