Extreme Mass-Ratio Inspiral Resonance Hunting
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Date
2024-05
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The Ohio State University
Abstract
Extreme mass-ratio inspirals (EMRIs) are systems with a compact object orbiting a much more massive body. They show up frequently in the literature of gravitational wave (GW) astronomy due to many theorists predicting that the future Laser Interferometer Space Antenna (LISA) will be able to hear stellar-mass compact objects falling into the supermassive black holes (SMBHs) at the centers of most large galaxies. This scenario is of interest both as a new probe of galactic nuclei and as a precision test of general relativity. This work focuses on the effects of an external perturbation on an EMRI system in the galactic center due to a third body. This perturbation will affect the orbit most significantly when the inner body crosses a resonance with the outer body, which results in a subsequent phase shift of the waveform that builds up over time. Resonances will cause measurable changes in the GW received by LISA. This thesis presents a general method for calculating the effects of a resonance on the orbits of the inner body. This is done by demonstrating that the orbital changes are related to the GWs emitted by the two bodies at the frequency corresponding to the resonance. This allows presented here allow for the reduction of a three-body system into a two-body system, with the third body being replaced by a gravitational wave perturbation, allowing us to sidestep using intense GR calculations. These methods will generate a more realistic waveform model, and provide a more accurate comparison for future detected signals. This work will be used in future investigations of third-body effects on EMRIs and their potential impact on GWs detected by LISA.