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Description
Current waveform models of binary black hole mergers incorporate a large amount of analytical information during the inspiral phase. On the other hand, post-merger templates use a phenomenological ansatz informed by numerical simulations, with the quasinormal frequencies as the only analytical input.
Working in the perturbative limit, we develop the first analytical model predicting the dynamical excitation of quasinormal modes during the plunge-merger-ringdown stages for generic orbits, including highly eccentric ones. We find that quasinormal mode amplitudes behave as activation functions near the waveform peak. Once the stationary ringdown regime is reached, a superposition of an infinite tower of non-oscillatory, exponentially damped terms appears. These terms are due to the source redshift at the horizon and can potentially swamp the overtone contributions. As a byproduct of our analysis, we explain from first principles the impact of the inspiral on the late-time, constant quasinormal mode amplitudes, which was previously observed a posteriori from numerical relativity fits.
Our model shows good agreement with a numerical solution of the binary merger. The proposed approach offers a highly promising way to extract physical quasinormal mode contributions, avoiding ambiguities and overfitting issues associated with phenomenological ansätze, and to construct analytically informed ringdown models.
