Visualizing 2PN Binary Black Hole Spin Precession*

In the post-Newtonian regime, the time it takes the two black-holes to orbit each other is much shorter than the time it takes the spins and the orbital angular momentum to precess about the direction of the total angular momentum which, in turn, is much shorter than the time it takes the binary's orbit to shrink due to gravitational-wave emission. In short, the dynamics of precessing binary black holes have a strong timescale hierarchy. Given the variables identified in [1] that respect the timescale separation of the dynamics of precessing binary black holes (𝜉, J, S), we build an interactive 3D visualization routine in Python to explore spin precession. We report the discovery of configurations where one of the two spins oscillate from being completely aligned with the orbital angular momentum to being completely anti-aligned with it during a single precession cycle. Crucially, this “wide precession” happens on the short precession timescale and it is not a secular effect due to gravitational-wave radiation reaction.

[1] D. Gerosa, M. Kesden, PRD 92, 064016 (2015), arXiv:1506.03492 [gr-qc].