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Numerical modelling of black-hole-binary mergers

Khan, Sebastian 2016. Numerical modelling of black-hole-binary mergers. PhD Thesis, Cardiff University.
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Abstract

The beginning of gravitational wave astronomy started on September 14th 2015 [13]. The event, GW150914, was so loud that the distinct morphological features indicative of the merger of two inspiraling black holes was difficult to deny. The estimation of source parameters and parameterised tests of general relativity in the strong field regime require the use of gravitational waveform models that predict the inspiral, merger and ringdown of binary black holes according to general relativity. This thesis is focused on providing the gravitational wave community with an accurate model for the gravitational wave signal emitted by coalescing, non-precessing binary black holes covering the inspiral, merger and ringdown. The solutions to the Einstein equations for the late inspiral, merger and ringdown of binary black holes can only be obtained by using numerical relativity. However, the computational cost of a single simulation is on the order of weeks to months and prohibits a dense sampling of the parameter space. Our method is founded on the phenomenological modelling program, which was specifically designed to directly incorporate results from numerical relativity and analytic approximations to construct global models across the parameter space for gravitational wave searches. We have refined the phenomenological method and developed a new waveform model, IMRPhenomD, which is suitable not only for gravitational wave searches but is also sufficiently accurate to be in used to estimate the parameters of gravitational wave candidate events without incurring large systematic uncertainties due to waveform modelling errors. Subsequent to the work presented here our waveform model was also extended to include the effects of precession, which was used in the analysis of advanced LIGO data during its first observing run (2015-2016), including the analysis of GW150914. We evaluate the current state of the field of waveform modelling by performing numerous comparisons between leading inspiral, merger and ringdown waveform models and find that independently developed models are largely in agreement. This builds confidence in our models when we use them outside of their respective calibration regions. However, there are still large regions of parameter space where the models are in disagreement and we highlight these regions as urgent targets for new numerical relativity simulations.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: Gravitational waves Phenomenological waveform waveform models inspiral
Funders: STFC
Date of First Compliant Deposit: 15 August 2016
Last Modified: 18 Aug 2021 13:28
URI: http://orca.cardiff.ac.uk/id/eprint/93841

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