Extreme mass-ratio inspirals as probes of scalar fields: eccentric equatorial orbits around Kerr black holes

TL;DR

This paper investigates how scalar fields influence the gravitational wave signals from extreme mass ratio inspirals around Kerr black holes, focusing on eccentric equatorial orbits and LISA's detection prospects.

Contribution

It models the impact of scalar charges on orbital evolution and waveforms in eccentric equatorial inspirals, extending previous work to more general orbital configurations.

Findings

Scalar charge significantly alters orbital evolution.

Waveform modifications depend on eccentricity and black hole spin.

LISA can potentially detect or constrain scalar charges.

Abstract

We study binary systems in which a stellar mass compact object spirals into a massive black hole, known as extreme mass ratio inspirals, in scenarios with a new fundamental scalar field. Earlier work has shown that, in most interesting such scenarios and to leading order in the mass ratio, the massive black holes can be adequately approximated by the Kerr metric and the imprint of the scalar field on the waveform is fully controlled by the scalar charge of the stellar mass object. Here we use this drastic simplification in the inspiral modelling and consider eccentric equatorial orbits. We study how the scalar charge affects the orbital evolution for different eccentricities and different values of the black hole spin. We then determine how changes in the orbital evolution get imprinted on the waveform and assess LISA's capability to detect or constrain the scalar charge.