Oscillations in the EMRI gravitational wave phase correction as a probe of reflective boundary of the central black hole

TL;DR

This paper explores how reflective boundary conditions at a black hole's horizon in extreme mass-ratio inspirals cause oscillations in gravitational wave phase, offering a potential observational probe for exotic compact objects.

Contribution

It introduces a model for gravitational wave phase modifications caused by reflective boundaries, highlighting their detectability with future space-based detectors.

Findings

Oscillations in energy flux modulate gravitational wave phase.

Phase modifications are detectable by future space-borne detectors.

Reflective boundary conditions produce distinct oscillatory signatures.

Abstract

We discuss the energy loss due to gravitational radiation of binaries composed of exotic objects whose horizon boundary conditions are replaced with reflective ones. Our focus is on the extreme mass-ratio inspirals, in which the central heavier black hole is replaced with an exotic compact object. We show, in this case, a modulation of the energy loss rate depending on the evolving orbital frequency occurs and leads to two different types of modifications to the gravitational wave phase evolution; the oscillating part directly corresponding to the modulation in the energy flux, and the non-oscillating part coming from the quadratic order in the modulation. This modification can be sufficiently large to detect with future space-borne detectors.