Toward efficient effective-one-body models for generic, nonplanar orbits

Complete waveform models able to account for arbitrary nonplanar orbits represent a holy grail in current gravitational-wave astronomy. Here, we take a step toward this direction and present a simple yet efficient prescription to obtain the evolution of the spin vectors and of the orbital angular momentum along noncircularized orbits, that can be applied to any eccentric aligned-spins waveform model. The scheme employed is motivated by insights gained from the post-Newtonian (PN) regime. We investigate the phenomenology of the Euler angles characterizing the time-dependent rotation that connects the coprecessing frame to the inertial one, gauging the importance of noncircular terms in the evolution of the spins of a precessing binary. We demonstrate that such terms are largely negligible, irrespectively of the details of the orbit. Such insights are confirmed by studying the radiation-frame of a few eccentric, precessing numerical relativity (NR) simulations. Our investigations confirm that the usual "twisting" technique employed for quasispherical systems can be safely applied to noncircularized binaries. By then augmenting a state-of-the-art effective-one-body (EOB) model for noncircular planar orbits with the prescription discussed, we obtain an inspiral-merger-ringdown (IMR) model for eccentric, precessing binary black holes (BBHs). We validate the model in the quasispherical limit via mismatches and present one phasing comparison against a precessing, eccentric simulation from the RIT catalog.