An all-sky survey in hard X-rays (1-20 keV) with the HEAO-1 satellite and further observations in the optical resulted in a catalog of about 700 X-ray sources with known optical counterparts (Remillard et al. 1992). This sample includes 43 Cataclysmic Variables (CVs), which are binaries consisting of a detached white-dwarf and a Roche lobe filling companion star. This thesis consists of studies of the X-ray selected sample of CVs. This thesis consists of 4 parts: (1) Classification. Each of the newly discovered CVs is studied, with the hope of determining its membership in one of five CV subclasses: nova-like, dwarf nova, high state, DQ Her and AM Her. (2) Class properties. Optically-thin accretion disk models are found to successfully model the emission line strengths, but only for those spectra in which the equivalent widths of all lines are greater than 20A. (3) Detailed studies of individual systems: H1752+081, H0538+608 (BY Cam). (4) Theoretical models of CV evolution and magnetic interactions. We have used a preexisting bi-polytrope code (Rappaport, Verbunt, and Joss 1983) to study the effects of different initial conditions on binary evolution. We show that CVs detected in the period gap, such as H0709-360, may be the result of a low initial mass of the secondary. I have extended the code of Rappaport et al., to study the time history of the white-dwarf spin period under the effects of the accretion torque and the MHD torque of Lamb et al. (1983). We follow the spin rate for an ensemble of magnetic field strengths of both stars. We find that for much of parameter space, magnetic CVs are asynchronous above the gap (DQ Her) and synchronized below the gap (AM Her). (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA. 02139-4307. Ph. 617-253-5668; Fax 617 -253-1690.) (Abstract shortened with permission of school.).
- Pub Date:
- January 1992
- Physics: Astronomy and Astrophysics