We evolve a set of 32 equal-mass black-hole binaries with collinear spins ( with intrinsic spin magnitudes | \vec { S } _ { 1 , 2 } / m ^ { 2 } _ { 1 , 2 } | = 0.8 ) to study the effects of precession in the highly nonlinear plunge and merger regimes .
We compare the direction of the instantaneous radiated angular momentum , \widehat { \delta J } _ { rad } ( t ) , to the directions of the total angular momentum , \hat { J } ( t ) , and the orbital angular momentum , \hat { L } ( t ) .
We find that \widehat { \delta J } _ { rad } ( t ) approximately follows \hat { L } throughout the evolution .
During the orbital evolution and merger , we observe that the angle between \vec { L } and total spin \vec { S } is approximately conserved to within 1 ^ { \circ } , which allows us to propose and test models for the merger remnant ’ s mass and spin .
For instance , we verify that the hangup effect is the dominant effect and largely explains the observed total energy and angular momentum radiated by these precessing systems .
We also verify that the total angular momentum , which significantly decreases in magnitude during the inspiral , varies in direction by less than \sim 5 ^ { \circ } .
The maximum variation in the direction of \vec { J } occurs when the spins are nearly antialigned with the orbital angular momentum .
Based on our results , we conjecture that transitional precession , which would lead to large variations in the direction of \vec { J } , is not possible for similar-mass binaries and would require a mass ratio m _ { 1 } / m _ { 2 } \lesssim 1 / 4 .