  Dynamical capture is a possible formation channel for BBH mergers leading to
highly eccentric merger dynamics and to gravitational wave (GW) signals that
are morphologically different from those of quasi-circular mergers. The future
detection of these mergers by ground-based or space-based GW interferometers
can provide invaluable insights on astrophysical black holes, but it requires
precise predictions and dedicated waveform models for the analysis. We present
a state-of-the-art effective-one-body (EOB) model for the multipolar
merger-ringdown waveform from dynamical capture black-hole mergers with
arbitrary mass-ratio and nonprecessing spins. The model relies on analytical
descriptions of the radiation reaction and waveform along generic orbits that
are obtained by incorporating generic Newtonian prefactors in the expressions
used in the quasi-circular case. It provides a tool for generating waveforms
for generic binary black hole coalescences and for GW data analysis. We
demonstrate that the model reliably accounts for the rich phenomenology of
dynamical captures, from direct plunge to successive close encounters up to
merger. The parameter space is fully characterized in terms of the initial
energy and angular momentum. Our model reproduces to few percent the scattering
angle from ten equal-mass, nonspinning, hyperbolic encounter
numerical-relativity (NR) simulations. The agreement can be further improved to
the by incorporating 6PN-results in one of the EOB potentials and tuning
currently unknown analytical parameters. Our results suggest that NR
simulations of hyperbolic encounters (and dynamical captures) can be used to
inform EOB waveform models for generic BBH mergers/encounters for present and
future GW detectors.
