Gravitational waves from the late inspiral, transition, and plunge of small-mass-ratio eccentric binaries

TL;DR

This paper models gravitational waves from small-mass-ratio eccentric black hole binaries during late inspiral and plunge, analyzing how eccentricity and orbital phase influence quasinormal mode excitation and waveform features.

Contribution

It develops a method to compute full inspiral and plunge trajectories for eccentric binaries and analyzes their gravitational wave signatures, including mode excitation and tail effects.

Findings

Eccentricity amplifies late-time power-law tails in waveforms.

Quasinormal mode excitation varies with orbital parameters.

Eccentricity effects on waveforms depend on orbital anomaly angle.

Abstract

Black hole binaries with small mass ratios will be important sources for the forthcoming Laser Interferometer Space Antenna (LISA) mission. Models of such binaries also serve as useful tools for understanding the dynamics of compact binary systems and the gravitational waves they emit. Using an eccentric Ori-Thorne procedure developed in previous work, we build worldlines that describe the full inspiral and plunge of a small body on an initially eccentric orbit of a Kerr black hole. We now calculate the gravitational waves associated with these trajectories using a code that solves the Teukolsky equation in the time domain. The final cycles of these waveforms, the ringdown, contain a superposition of Kerr quasinormal modes followed by a power-law tail. In this paper, we study how a binary's eccentricity and orbital anomaly angle affect the excitation of both quasinormal modes and late-time tails. We find that the relative excitation of quasinormal modes varies in an important and interesting way with these parameters. For some anomaly angles, the relative excitations of quasinormal modes are essentially indistinguishable from those excited in quasi-circular coalescences. Consistent with other recent studies, we find that eccentricity tends to amplify the late-time power-law tail, though the amount of this amplification varies significantly with orbital anomaly. We thus find that eccentricity has an important impact on the late-time coalescence waveform, but the interplay of eccentricity and orbit anomaly complicates this impact.