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Abstract

We investigate the late-time tail behavior in gravitational waves from
merging eccentric binary black holes (BBH) using black hole perturbation
theory. For simplicity, we focus only on the dominant quadrupolar mode of the
radiation. We demonstrate that such tails become more prominent as eccentricity
increases. Exploring the phenomenology of the tails in both spinning and
non-spinning eccentric binaries, with the spin magnitude varying from
$\chi=-0.6$ to $\chi=+0.6$ and eccentricity as high as $e=0.98$, we find that
these tails can be well approximated by a slowly decaying power law. We study
the power law for varying systems and find that the power law exponent lies
close to the theoretically expected value $-4$. Finally, using both plunge
geodesic and radiation-reaction-driven orbits, we perform a series of numerical
experiments to understand the origin of the tails in BBH simulations. Our
results suggest that the late-time tails are strongly excited in eccentric BBH
systems when the smaller black hole is in the neighborhood of the apocenter, as
opposed to any structure in the strong field of the larger black hole. Our
analysis framework is publicly available through the \texttt{gwtails} Python
package.