Unambiguous Determination of Gravitational Waveforms from Binary Black Hole Mergers

Gravitational radiation is properly defined only at future null infinity (J+), but in practice it is estimated from data calculated at a finite radius. We have used characteristic extraction to calculate gravitational radiation at J+ for the inspiral and merger of two equal-mass nonspinning black holes. Thus we have determined the first unambiguous merger waveforms for this problem. The implementation is general purpose and can be applied to calculate the gravitational radiation, at J+, given data at a finite radius calculated in another computation.