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Accurate identification of the nature of signals in ground-based gravitational-wave interferometer data

Relton, Philip 2023. Accurate identification of the nature of signals in ground-based gravitational-wave interferometer data. PhD Thesis, Cardiff University.
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The data from ground-based gravitational-wave interferometers has been used for direct astrophysical observations of transient signals for almost a decade. With this data, over 90 compact binary systems have been observed and studied via their gravitational-wave emission. These observations have, and continue to, provide new solutions to astrophysical questions. Gravitational waves can provide information about astrophysical systems that has previously been inaccessible through electromagnetic observations. The aim of this thesis is to outline some of the dangers of making incorrect assumptions about observed signals in gravitational-wave interferometer data. In Chapter 1 I provide a summary of gravitational-wave interferometer data; from the basic design of the interferometers, through the form of the data, and some methods can be used to manipulate the data for analysis. I then describe the types of signals that can be observed in this data, how these signals are studied, and what further analysis can be performed on the results of these studies. In Chapter 2 I calculate the probability that transient gravitational-wave signals will overlap with each other in the data. In the chapters that follow I outline the potential problems that time-overlapping transients will cause for the signal detection and analysis methods currently implemented by the LIGO-Virgo-KAGRA collaboration. Chapter 3 shows how the presence of a second, time-overlapping, binary black hole signal can cause inaccuracies in the estimation of the parameters of the other binary black hole system. I show how this problem manifests in the estimated parameter distributions for different relative parameters between two compact binary signals. In Chapters 4 and 5 I consider whether it is possible to detect these cases of time-overlapping transients with current methods, determining what cases will be missed without modifications to current algorithms. I also discuss possible modifications to these algorithms, and a separate bespoke method, designed to identify which detected signals contain time-overlapping transient signals. Chapter 6 presents an analysis of the data of a gravitational-wave interferometer for the purposes of a search for scalar dark matter signals. In this work, we produced extremely precise estimations of the noise floor of the interferometer. We used this to identify and reject possible candidate signals from scalar dark matter. Finally, in Chapter 7, I provide a summary of the key findings in each of the chapters of this thesis. This chapter includes recommendations of extensions and adaptations to the described investigations to expand and improve upon this work.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: 4. Gravitational wave, transient signals, time overlapping, Bayesian inference, stochastic sampling, matched filter searches, scalar dark matter, data analysis
Funders: STFC
Date of First Compliant Deposit: 15 June 2023
Last Modified: 15 Jun 2023 09:40

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