Gravitational waves from Extreme Mass Ratio Inspirals in non-pure Kerr spacetimes

TL;DR

This study explores how the presence of a massive torus around a black hole affects gravitational wave signals from extreme mass-ratio inspirals, revealing potential challenges in distinguishing these signals from pure Kerr black holes.

Contribution

It provides the first detailed analysis of gravitational waveforms from EMRIs in non-pure Kerr spacetimes with a self-gravitating torus, highlighting the potential for waveform confusion.

Findings

Most waveforms are indistinguishable from pure Kerr signals.

A significant parameter space exists where detection of deviations is challenging.

Confusion problems may occur in gravitational wave observations with LISA.

Abstract

To investigate the imprint on the gravitational-wave emission from extreme mass-ratio inspirals in non-pure Kerr spacetimes, we have studied the ``kludge'' waveforms generated in highly-accurate, numerically-generated spacetimes containing a black hole and a self-gravitating, homogeneous torus with comparable mass and spin. In order to maximize their impact on the produced waveforms, we have considered tori that are compact, massive and close to the central black hole, investigating under what conditions the LISA experiment could detect their presence. Our results show that for a large portion of the space of parameters the waveforms produced by EMRIs in these black hole-torus systems are indistinguishable from pure-Kerr waveforms. Hence, a ``confusion problem'' will be present for observations carried out over a timescale below or comparable to the dephasing time.