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Photometric Mass Determinations of Eclipsing Cataclysmic Variables

McAllister, Martin J. (2017) Photometric Mass Determinations of Eclipsing Cataclysmic Variables. PhD thesis, University of Sheffield.

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Abstract

Cataclysmic variables (CVs) are a type of close, interacting binary system containing a white dwarf primary and a low-mass, Roche lobe-filling secondary/donor. Mass is commonly transferred from the donor to an accretion disc around the white dwarf, due to the conservation of angular momentum, before eventually reaching the surface of the white dwarf. A region of increased luminosity, termed the 'bright spot', exists at the intersection of accretion disc and mass transfer stream. The transfer of mass within the system is a turbulent process, giving rise to random photometric variations commonly referred to as 'flickering'. For high inclination systems, the donor eclipses all other components within the system, resulting in complex eclipse light curves that can be fit with a parameterised model to obtain system parameters. Eclipses of the white dwarf and bright spot occur in quick succession, and therefore precise eclipse modelling requires high-time-resolution photometry. Flickering is a hindrance to eclipse modelling, however, as it can obscure ingress/egress features of the component eclipses, and therefore existing studies use eclipse averaging to minimise its effects. In this thesis, a new approach to eclipse modelling is introduced, which involves modelling flickering through the utilisation of Gaussian processes (GPs). The new modelling approach is implemented on ULTRACAM/ULTRASPEC eclipse light curves of 18 eclipsing CVs, returning 18 sets of precise system parameters. Four of these systems have been modelled previously using the existing approach, while 14 are modelled for the first time. The 18 new/revised white dwarf and donor masses from this work are used alongside other CV component masses from the literature in an attempt to secure a better understanding of CVs and their evolution. One of the outcomes is a new estimate for the CV orbital period minimum, 79.57+-0.22 min, which is over 2 min shorter than previously thought.

Item Type: Thesis (PhD)
Academic Units: The University of Sheffield > Faculty of Science (Sheffield) > Physics and Astronomy (Sheffield)
Identification Number/EthosID: uk.bl.ethos.736558
Depositing User: Mr Martin McAllister
Date Deposited: 14 Mar 2018 12:13
Last Modified: 12 Oct 2018 09:52
URI: http://etheses.whiterose.ac.uk/id/eprint/19647

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