A survey of cataclysmic variables from the Edinburgh-Cape Blue object survey
Doctoral Thesis
1994
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University of Cape Town
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Abstract
This thesis is based on the Edinburgh-Gape Blue Object Survey and includes a general review of blue star sky surveys, a detailed discussion of the selection techniques, the present status of the survey, and follow-up photometry and spectroscopy of the cataclysmic variable stars (GVs) found by the survey. Because of the north-south imbalance in the number of blue objects, the Edinburgh-Gape Blue Object survey was designed to discover previously unknown blue objects with B≤~18 at high galactic latitude in the southern hemisphere. At present, all the planned fields (61 fields) in the North Galactic Pole region and 26 fields in the South Galactic Pole regions are complete, covering 2488 square degrees. The preliminary results show that the survey has an internal completeness of ~94% for objects with U-B bluer than the cutoff --0.3, and selects objects with an accuracy in photographic U-B of 0.16 mag. UBV measurements and spectra have been obtained for ~2000 objects. Half of these objects are hot subdwarfs which comprise the sdO, sdB, and sdOB stars. The white dwarfs account for about 17% of the total. About 18% of the objects are horizontal branch B and normal B stars. Cataclysmic variable stars and quasars comprise only a small fraction, 2 and 6 percent, respectively. Less than one percent are galaxies. The remaining ~5% have unknown spectral classes at present. So far, 25 cataclysmic variable stars have been found by the survey. The space density was estimated to be 1.6xl0-⁶ pc-³. Among these cataclysmic variables, 6 dwarf novae and 8 nova-like variables are new discoveries; detailed study of their photometric and spectroscopic characteristics are discussed in Chapters 6-10. One of the stars discovered, a close binary with large reflection effect, is a predecessor of the cataclysmic variables. Napier's (1968) method for the reflection effect in close binaries was used to model the light curve in order to solve for the physical properties of the system. Photometry, spectroscopy, and model fits for this system are discussed in Chapter 5.
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Includes bibliographical references.
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Reference:
Chen, A. 1994. A survey of cataclysmic variables from the Edinburgh-Cape Blue object survey. University of Cape Town.