# Tail wavelets in the merger of binary compact objects

## TL;DR

This paper proposes a model where dark matter surrounding merging compact objects causes tail wavelets in gravitational wave signals, explaining their origin within general relativity without new physics.

## Contribution

The study introduces a simplified model showing how dark matter can generate tail wavelets after binary mergers, highlighting differences between dressed and bare black holes.

## Key findings

- Dark matter can produce tail wavelets following gravitational wave ringdown.
- Radiation pressure from the main wave can displace surrounding matter, causing tail wavelets.
- The effect of dark matter's back reaction on the tail wavelet is negligible.

## Abstract

We present a model for tail wavelets, a phenomenon also known as "echo" in the literature. The tail wavelet may appear in signal reconnaissances in the merger of binary compact objects, including black holes and neutron stars. We show that the dark matter surrounding the compact objects lead to the speculated tail wavelet following the main gravitational wave (GW). We demonstrate that the radiation pressure of the main wave is fully capable of pushing away the the surrounding matter to some altitude, and splashing down of the matter excites the tail wavelet after ring down of the main wave. We illustrate this idea in a simplified model, where numerical estimations are carried out concerning the specific distribution of the dark matter outside the black hole horizon and the threshold values in accordance with observations. We study the full back reaction of the surrounding dark matter to the metric, and find that the effect is insignificant to the tail wavelets. We find the fine difference between the tail wavelets of a dressed black hole and a bare one. We demonstrate that the tail wavelet can be a natural phenomenon in frame of general relativity, without invoking any modified gravities or quantum effects.