Rotating black holes experience dynamical tides

TL;DR

This paper calculates the dynamical tidal response of Kerr black holes, showing they have non-zero tidal Love numbers under certain conditions, which impacts gravitational wave data interpretation.

Contribution

It demonstrates that Kerr black holes possess non-zero dynamical tidal Love numbers, revealing they are deformable in non-axisymmetric, time-dependent external fields.

Findings

Kerr black holes have non-zero tidal Love numbers.

Tidal Love numbers depend quadratically on spin and linearly on mode frequency.

Implications for gravitational wave analysis and black hole identification.

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.