Quasinormal modes and their overtones at the common horizon in a binary black hole merger

Understand

It is expected that all astrophysical black holes in equilibrium are well described by the Kerr solution.

• Moreover, any black hole far away from equilibrium, such as one initially formed in a compact binary merger or by the collapse of a massive star, will eventually reach a final equilibrium Kerr state.
• At sufficiently late times in this process of reaching equilibrium, we expect that the black hole is modeled as a perturbation around the final state.
• The emitted gravitational waves will then be damped sinusoids with frequencies and damping times given by the quasinormal mode spectrum of the final Kerr black hole.