  We study nonlinear evolutions of binary black hole mergers, uncovering
power-law contributions generated by the long-range behaviour of the
highly-curved dynamical spacetime. The result is achieved by exploiting the
strong increase of the tail relevance due to binary eccentricity, recently
observed in perturbative evolutions of a small-mass-ratio binary under accurate
radiation reaction by Albanesi and collaborators [PhysRevD.108.084037]. We
demonstrate the presence of this enhancement even in the nonlinear case of
comparable-mass binary mergers in eccentric orbits, using the public RIT
waveform catalog. The instantaneous frequency of the simulations displays large
oscillations at intermediate to late-times, due to interference terms in the
transition between a fast-decaying, constant-frequency quasinormal-mode driven
regime, and a power-law, slowly-decaying one. The power-law exponent displays
broad convergence with perturbative predictions, although longer and more
accurate simulations will be needed to pinpoint the asymptotic value. Our
results offer yet another confirmation of the highly predictive power of black
hole perturbation theory in the presence of a source, even when applied to
nonlinear solutions. The magnitude of the tail signal is within reach of
gravitational-wave detectors measurements, unlocking the possibility of
observationally investigating an additional set of general relativistic
predictions on the long-range dynamics of relaxing compact objects.
