Probing the system parameters of cataclysmic variable stars
Probing the system parameters of cataclysmic variable stars
Cataclysmic Variables (CVs) are close binary stars in which a low mass star is losing material onto its companion, a white dwarf, via an accretion disc. This thesis presents an analysis of the optical spectra of these objects.
New orbital parameters are presented for a particular system, EM Cygni, which was previously thought to contain a white dwarf accreting material from a less-massive companion, a dynamically unstable configuration which should not have existed according to theory. The new parameters remove the instability, which was due to spectral contamination from a third star, but introduce a further dilemma; is this third star physically associated with the CV?
Accurate centre-of-mass velocities are calculated for four CVs as an initial step towards completing a full statistical analysis of this parameter for the CV population. These are to be used as a direct test of the magnetic braking mechanism, an essential part of the present theory describing CV evolution.
Measurements of the outer velocities of the accretion discs in Dwarf Novae (DN, a subclass of CVs) and in a related group of interacting binary stars the Soft X-ray Transients (SXTs), are analysed to compare with the theoretical predictions. This tests whether observations of SXTs support the irradiation model created to explain the outbursts in these systems. Initial results suggest the observations present difficulties for the irradiation model, as no discs are seen close to the theoretical circulations limit as is predicted from this theory.
Finally, the technique of Doppler tomography is applied to the Balmer Hα emission from long-period quiescent DN to discern its origins and to obtain accretion disc parameters. None of the resulting Doppler maps appear as predicted, reasons for this are discussed.
University of Southampton
North, Rachel Caroline
a2a7d442-556e-43b9-933d-94f1d7d94dd4
2001
North, Rachel Caroline
a2a7d442-556e-43b9-933d-94f1d7d94dd4
North, Rachel Caroline
(2001)
Probing the system parameters of cataclysmic variable stars.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Cataclysmic Variables (CVs) are close binary stars in which a low mass star is losing material onto its companion, a white dwarf, via an accretion disc. This thesis presents an analysis of the optical spectra of these objects.
New orbital parameters are presented for a particular system, EM Cygni, which was previously thought to contain a white dwarf accreting material from a less-massive companion, a dynamically unstable configuration which should not have existed according to theory. The new parameters remove the instability, which was due to spectral contamination from a third star, but introduce a further dilemma; is this third star physically associated with the CV?
Accurate centre-of-mass velocities are calculated for four CVs as an initial step towards completing a full statistical analysis of this parameter for the CV population. These are to be used as a direct test of the magnetic braking mechanism, an essential part of the present theory describing CV evolution.
Measurements of the outer velocities of the accretion discs in Dwarf Novae (DN, a subclass of CVs) and in a related group of interacting binary stars the Soft X-ray Transients (SXTs), are analysed to compare with the theoretical predictions. This tests whether observations of SXTs support the irradiation model created to explain the outbursts in these systems. Initial results suggest the observations present difficulties for the irradiation model, as no discs are seen close to the theoretical circulations limit as is predicted from this theory.
Finally, the technique of Doppler tomography is applied to the Balmer Hα emission from long-period quiescent DN to discern its origins and to obtain accretion disc parameters. None of the resulting Doppler maps appear as predicted, reasons for this are discussed.
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Published date: 2001
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Local EPrints ID: 464440
URI: http://eprints.soton.ac.uk/id/eprint/464440
PURE UUID: 6203ac9c-8e2a-4725-97d9-3deed4f519bf
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Date deposited: 04 Jul 2022 23:38
Last modified: 16 Mar 2024 19:31
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Author:
Rachel Caroline North
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