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Modelling and studying gravitational waves from black-hole-binary mergers

Kalaghatgi, Chinmay ORCID: 2019. Modelling and studying gravitational waves from black-hole-binary mergers. PhD Thesis, Cardiff University.
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The source parameters of the first direct detection (GW150914 [3]) of gravitational waves (GW) from a binary black hole (BBH) system were determined by using approximate models of the BBH coalescence, the errors on which could be driven by the noise (statistical errors) or the approximate nature of the model (systematic errors). To determine the systematic errors, a set of numerical relativity (NR) waveforms with similar parameters as of GW150914 were injected over a range of inclination and polarisation values and recovered with IMRPhenomPv2. The main result of this study was that the systematic errors induced due to waveform model inaccuracies were much smaller than corresponding statistical errors, and hence, the statistical errors dominate the systematic for the inferred parameters of GW150914. For current precessing waveform models, the six dimensional spin space is mapped to a two dimensional space of effective spin parameters. We investigate the effects of changing the in-plane spin direction on the GW signal and determine whether these effects are strong enough to be measured by current ground based GW detectors. We also study the effect of disregarding the mode-asymmetry content present in the signals and attempt to answer whether mode-asymmetries need to be included in future waveform models. GW signals, when decomposed in the spin weighted spherical harmonic basis, are made of its different modes (hlms), with the quadrupole mode being dominant. The waveform model IMRPhenomHM models a few of the sub-dominant modes with the quadrupole mode for aligned-spin binaries. We wanted to investigate the effects of using a multimode (IMRPhenomHM) and quadrupole only (IMRPhenomD) waveform model to recover source parameters from multimode signals (IMRPhenomHM signals) and real physical signals (NR waveform signals) across a range of physical parameters and inclination values.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Uncontrolled Keywords: Gravitational Waves, Binary Black Holes, Precessing systems, Precession, Higher-order Modes, Parameter Estimation, Numerical Relativity
Funders: European Research Council
Date of First Compliant Deposit: 14 January 2020
Last Modified: 07 Nov 2022 09:16

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