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Abstract

Waveform models are essential for gravitational-wave (GW) detection and
parameter estimation of coalescing compact-object binaries. More accurate
models are required for the increasing sensitivity of current and future GW
detectors. The effective-one-body (EOB) formalism combines the post-Newtonian
(PN) and small mass-ratio approximations with numerical-relativity results, and
produces highly accurate inspiral-merger-ringdown waveforms. In this paper, we
derive the analytical precessing-spin two-body dynamics for the
\texttt{SEOBNRv5} waveform model, which has been developed for the upcoming
LIGO-Virgo-KAGRA observing run. We obtain an EOB Hamiltonian that reduces to
the exact Kerr Hamiltonian in the test-mass limit. It includes the full 4PN
precessing-spin information, and is valid for generic compact objects (i.e.,
for black holes or neutron stars). We also build an efficient and accurate EOB
Hamiltonian that includes partial precessional effects, notably orbit-averaged
in-plane spin effects for circular orbits, and derive 4PN-expanded
precessing-spin equations of motion, consistent with such an EOB Hamiltonian.
The results were used to build the computationally-efficient precessing-spin
multipolar \texttt{SEOBNRv5PHM} waveform model.