We present the IMRPhenomXE frequency-domain phenomenological waveform model for the dominant mode of inspiral-merger-ringdown non-precessing binary black holes in elliptical orbits. IMRPhenomXE extends the quasi-circular IMRPhenomXAS waveform model for the dominant (ℓ,∣m∣)= (2,2) modes to eccentric binaries. For the inspiral part, orbit-averaged equations of motion within the quasi-Keplerian parametrization up to third post-Newtonian order, including spin effects, are evolved, and the waveform modes are computed using the stationary phase approximation on eccentricity expanded expressions up to O(e12). The model assumes circularization at merger-ringdown, where it adopts the underlying quasicircular IMRPhenomXAS baseline. We show that IMRPhenomXE reduces to the accurate IMPhenomXAS model in the quasi-circular limit. Compared against 186 public numerical relativity waveforms from the Simulating eXtreme Spacetimes catalog with initial eccentricities up to 0.8, IMRPhenomXE provides values of unfaithfulness below 3% for 72% of simulations with initial eccentricities below 0.4. For larger eccentricities, the unfaithfulness degrades up to ≳10% due to the underlying small eccentricity expansions and additional modelling approximations. In terms of speed, IMRPhenomXE outperforms any of the existing inspiral-merger-ringdown eccentric waveform models. We demonstrate the efficiency, robustness, and modularity of IMRPhenomXE through injections into zero noise and parameter-estimation analyses of gravitational-wave events, showing that IMRPhenomXE is a ready-to-use waveform model for gravitational-wave astronomy in the era of rapidly growing event catalogs.
@article{arxiv.2601.03340,
title = {Fast frequency-domain phenomenological modeling of eccentric aligned-spin binary black holes},
author = {Antoni Ramos-Buades and Quentin Henry and Maria Haney},
journal= {arXiv preprint arXiv:2601.03340},
year = {2026}
}