Modeling the merger-ringdown of an eccentric test-mass inspiral into a Kerr black hole using the effective-one-body framework

TL;DR

This paper develops a phenomenological model for the merger-ringdown gravitational wave signal from eccentric inspirals into Kerr black holes, incorporating eccentricity effects and quasinormal mode mixing.

Contribution

It introduces a new merger-ringdown model for eccentric inspirals within the effective-one-body framework, extending waveform modeling capabilities for gravitational wave analysis.

Findings

Eccentricity mainly affects the last peak features of the waveform.

Relativistic anomaly influences the last peak morphology but not the ringdown.

The model accounts for quasinormal mode mixing during ringdown.

Abstract

We characterize and phenomenologically model the merger-ringdown of gravitational waves emitted by a small compact object that plunges and merges into a Kerr black hole from equatorial-eccentric inspirals. The waveforms are generated employing a time-domain Teukolsky code sourced with trajectories computed using the effective-one-body framework. We span values of the Kerr spin $a\in[-0.9, 0.9] $, eccentricity at the last stable orbit (LSO) $ e_{\rm LSO} \in [0,0.9] $, and relativistic anomaly $ \xi_{\rm LSO} \in [0 , 2 \pi]$. We characterize the last peak of the waveform and ringdown features across the parameter space, finding that the eccentricity mainly affects the last peak features, while it has a smaller impact on the ringdown signal. In contrast, the relativistic anomaly measured at the LSO influences the morphology of the last peak in a restricted portion of the parameter space and has no impact on the ringdown part. We perform the analysis for all the spin-weighted spherical harmonic modes normally included in the $\texttt{SEOBNR}$ family of models, $(\ell,m)\in\{ (2,2), (3,3), (4,4), (5,5), (2,1), (3,2), (4,3)\}$. Finally, we introduce a merger-ringdown model for $\texttt{SEOB-TMLE}$, a forthcoming inspiral-merger-ringdown waveform model for eccentric spin-aligned binary black holes in the test-mass limit, whose features can be extended to comparable-mass regimes. The model also accounts for quasinormal mode mixing during the ringdown. It provides a first step toward incorporating the impact of residual eccentricity close to merger into spin-aligned effective-one-body merger-ringdown models for binary black holes.