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Multi-wavelength studies of non-magnetic cataclysmic variables

Dickinson, Rachel Joanna; (1997) Multi-wavelength studies of non-magnetic cataclysmic variables. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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This thesis comprises spectroscopic case studies of three non-magnetic nova-like and dwarf nova type cataclysmic variables (CVs). The principal goals were to investigate the accretion disk and optical spectral line properties of a sample of CVs which are known (usually from ultraviolet studies) to drive a fast outflow or wind. New optical, time-series data sets, secured from La Palma and Canada, are used to establish the (often complex) time- and phase-dependent behaviour of the emission and absorption line sources. The optical analyses have also been compared and contrasted with constraints from Hubble Space Telescope (HST) and archive International Ultraviolet Explorer (IUE) data. High resolution optical spectroscopy of V795 Herculis is presented. Separate low and high velocity fluctuations phased on the 2.6 hr orbital period are observed in the Balmer lines. This thesis argues against models which invoke channelled accretion columns flowing onto a synchronously rotating white dwarf, instead presenting disk-overflow model simulations which quantitatively account for several of the observed dynamical properties of V795 Her. The discrepancies of this model are addressed. A comparison of these optical spectra to quasi-simultaneous HST observations (which provide an unprecedented multi-wavelength data set) is made. A strong correlation between the overall UV and optical line strength changes implies that the UV changes cannot be principally due to the fast outflow. A time-resolved orbital study of the dwarf nova SS Cygni is also presented. These observations were taken at the maximum of a long, asymmetric type outburst, and confirm the presence of stationary, low velocity emission previously reported during a long, symmetric outburst. Possible sources for this emission, including a wind origin, are investigated. The peculiar nova-like BZ Camelopardalis, associated with a bow-shock nebula, has previously shown unambiguous evidence for a wind in its optical spectrum. New optical data reveal wind-formed features in the Balmer lines. Model fits constrain the inclination angle and archive IUE spectra are used to estimate the wind mass loss.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Multi-wavelength studies of non-magnetic cataclysmic variables
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Pure sciences; Cataclysmic variables
URI: https://discovery.ucl.ac.uk/id/eprint/10097528
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