Figure 13: Final spin of a remnant black hole in terms of its original spin, for mass ratios (red), (green) and (blue). The change in spin was computed using the test-particle approximation for [16, 91, 227]. Upper (lower) curves correspond to prograde (retrograde) capture from the equatorial plane; dashed curves are for capture over the pole. Capture of a low-mass secondary is likely to spin down the larger hole unless the latter is slowly rotating initially. Capture of a massive secondary results in spinup unless infall is nearly retrograde or the original spin is large.