Faithful effective-one-body waveform of small-mass-ratio coalescing black hole binaries: The eccentric, nonspinning case

We present a new effective-one-body (EOB) waveform for eccentric, nonspinning binaries in the extreme mass ratio limit, with initial eccentricities up to 0.95. The EOB analytical waveform, that includes noncircular corrections up to second post-Newtonian order, is completed by a phenomenological ringdown model that is informed by Regge-Wheeler-Zerilli (RWZ) type waveforms generated by a point-particle source. This model notably includes the beating between positive and negative frequency quasinormal modes (QNMs). We analyze various prescriptions to faithfully complete the analytical EOB waveform in the transition from plunge to merger. In particular, we systematically explore the effect of: (i) the generic Newtonian prefactor; (ii) next-to-quasicircular (NQC) corrections to amplitude and phase; (iii) the point where NQC corrections are determined; (iv) the ringdown attachment point. This yields EOB/ RWZ quadrupolar phase differences through merger and ringdown less than or similar to 0.01 rad for the quasicircular case and less than or similar to 0.05 rad for the eccentric case. Higher modes are also modeled up to the l = m = 5 multipole. We finally discuss the excitation of the QNMs and present a heuristic model to motivate it in correlation with the presence of a point-particle source.