Grazing Collisions of Black Holes via the Excision of Singularities

We present the first simulations of non-head-on (grazing) collisions of binary black holes in which the singularities are excised from the simulation. Initially equal mass $m$ black holes (spinning or not) are separated by $\approx 10m$ and with impact parameter $\approx 2m$. Evolutions to $t\approx 35m$ are obtained where two separate horizons are present for $t\approx 3.8m$; then a single enveloping horizon forms indicating that the holes merged. Apparent horizon area estimates suggest gravitational radiation of about $2\%–3\%$ of the total mass. The evolutions end after a moderate amount of time because of instabilities.