Quasinormal-mode filters: a new approach to analyze the gravitational-wave ringdown of binary black-hole mergers

Understand

We propose two frequency-domain filters to analyze ringdown signals of binary black hole mergers.

• The first rational filter is constructed based on a set of (arbitrary) quasi-normal modes (QNMs) of the remnant black holes, whereas the second full filter comes from the transmissivity of the remnant black holes.
• The two filters can remove corresponding QNMs from original time-domain ringdowns, while changing early inspiral signals in a trivial way - merely a time and phase shift.
• After filtering out dominant QNMs, we can visualize the existence of various subdominant effects.