Algebraic classification of numerical spacetimes and black-hole-binary remnants

In this paper we develop a technique for determining the algebraic classification of a numerically generated spacetime, possibly resulting from a generic black-hole-binary merger, using the Newman-Penrose Weyl scalars. We demonstrate these techniques for a test case involving a close binary with arbitrarily oriented spins and unequal masses. We find that, postmerger, the spacetime quickly approaches Petrov type II, and only approaches type D on much longer time scales. These techniques, in combination with techniques for evaluating acceleration and Newman-Unti-Tamburino parameters, allow us to begin to explore the validity of the ``no-hair theorem'' for generic merging-black-hole spacetimes.