Black Hole Ringdown Spirals

The post-merger of a binary black hole coalescence, known as the ringdown, provides important information about the remnant black hole. While dominated by quasi-normal mode emission at early times, the late time emission is governed by a power-law tail.

The amplitude and phase properties of the former are found by fitting to numerical relativity waveforms, while the latter are not typically extracted from such simulations due to extrapolation artifacts (except in rare cases). Most of these studies focus on fitting to either the gravitational wave polarizations or amplitude.

In this talk, I will instead focus on the instantaneous waveform phase, and show how it constitutes an attractor-repulsor system arising from the interference between quasi-normal modes and the power-law tail. I will discuss prospects for inferring the properties of the power-law tail in quasi-circular waveforms from numerical relativity, where they are buried beneath extraction artifacts.