Speaker
Description
Post-merger ringdown signals in compact-binary coalescences encode characteristic imprints of the underlying spacetime, traditionally described in terms of quasinormal modes. Motivated by a recently uncovered connection between post-merger black-hole signals and greybody factors, we investigate greybody factors as gravitational observables, providing a complementary approach to QNMs. We show that greybody factors remain stable under small perturbations and are not affected by several ambiguities that limit the robustness of a purely QNM-based description.
We then test this greybody factor–based framework against a broad set of numerical-relativity waveforms from the SXS catalog, focusing on comparable-mass binaries with generic spins. By extracting and fitting the frequency-domain ringdown signal across the catalog, we study how the model parameters vary throughout the binary parameter space. This allows us to assess the domain of validity of the approach, identify systematic trends linked to binary properties, and explore its potential as an alternative parametrization of ringdown signals for gravitational-wave data analysis.