Rotating black holes experience dynamical tides

Abstract: We find the dynamical tidal response of a Kerr black hole (BH) and demonstrate its tidal Love numbers to be non-vanishing when present in a non-axisymmetric external tidal field. To leading order, they depend quadratically on the black hole spin and linearly on the mode frequency. This implies that Kerr BHs are deformable under certain external, time-dependent perturbations. Since non-vanishing tidal Love numbers have been used in compact binary coalescences observed by the LIGO-Virgo-KAGRA (LVK) Collaboration to infer their non-BH nature, our findings have important implications on such inferences from future gravitational wave observations.