Practical formula for the radiated angular momentum

We present a simple formula for the radiated angular momentum based on a spin-weighted spherical harmonic decomposition of the Weyl scalar psi(4) representing outgoing radiation in the Kinnersley tetrad. We test our formula by measuring the radiated angular momentum from three simulations of nonspinning equal-mass-black-hole binaries with orbital angular momentum aligned along the x, y, and z axes, respectively. We find that the radiated angular momentum agrees with the differences in the remnant horizon spins and the initial angular momentum for each system.