Gravitational waves from extreme mass ratio inspirals in Kerr-MOG spacetimes

Abstract

This work elaborates on a detailed analysis of the novel characteristics of gravitational waves (GWs) generated by extreme mass-ratio inspirals (EMRIs) within the framework of modified gravity (MOG). Our study begins by exploring the geometrical and dynamical properties of the Kerr-MOG spacetime. We employ the numerical kludge (NK) method for waveform simulations and reveal that the parameter α, representing deviations from general relativity (GR), significantly impacts the frequencies of geodesic orbits and, consequently, the EMRI waveforms. However, the waveform confusion problem remains mainly unresolved, posing a challenge in distinguishing between the underlying gravitational theories based on the observed EMRI waveforms. Notably, by incorporating the effects of radiation reaction and increasing the MOG parameter α, we observe a substantial reduction in the waveform overlap over time. This reduction could enhance our ability to discern between different waveforms over an extended period. Our analysis further identifies that α begins to influence energy fluxes at the 1 post-Newtonian (PN) order, highlighting its leading-order effects on the orbital dynamics. Additionally, we find that α becomes detectable when the estimated overlap crosses the detection threshold by computing the mismatch. And we estimate that the detection error for α can be constrained to Δα ≈ 1.85 × 10-4 by using the Fisher information matrix (FIM) method, demonstrating the potential of space-based gravitational wave detectors to probe deviations from GR with high precision.