Tests for the existence of horizon through gravitational waves from a small binary in the vicinity of a massive object

TL;DR

This paper investigates whether gravitational wave signals from a small binary near a massive object can reveal the presence of an exotic compact object's horizon by analyzing continuous echo waves caused by reflectivity at the horizon.

Contribution

It introduces a method to detect ECO horizons using gravitational wave echoes from small binaries near massive objects, solving the Teukolsky equation with reflective boundary conditions.

Findings

Echo waves depend on the reflectivity of the ECO horizon

Continuous echoes can serve as probes for horizon existence

The approach provides a new observational test for exotic compact objects

Abstract

In this letter we calculate the gravitational waves (GWs) emitted from a small binary (SB) by solving the Teukolsky equation in the background of a massive exotic compact object (ECO) which is phenomenologically described by a Schwarzschild geometry with a reflective boundary condition at its "would-be" horizon. The "continuous echo" waves propagating to infinity due to reflectivity of ECO at its "would-be" horizon provide an exquisite probe to the nature of the ECO's horizon.