X-Ray and Ultraviolet Studies of the Interstellar Medium and the Winds of Cataclysmic Variables.

By means of an analysis of X-ray imaging data obtained with the Einstein Observatory, we present a study of the halos of Galactic X-ray sources produced by the scattering of X-rays by interstellar grains. The size, shape, and intensity of these X-ray halos are used to determine the parameters (e.g., the size distribution and number density) characterizing interstellar grains. In addition, we present an observational study of the X-ray halos of the four brightest young Galactic supernova remnants: the Crab Nebula, Cas A, Tycho's, and Kepler's supernova remnant; an observational and theoretical study of the purported soft X-ray halo around the dwarf nova SU UMa; and a theoretical study of the effect of the X-ray halo of the X-ray binary Cyg X-3 on the depth of modulation of this source's X-ray light curve and the impact of this effect on the stellar wind, cocoon, and accretion disk corona models for this source. In addition, by means of an analysis of the narrow absorption lines in high-resolution ultraviolet spectra obtained with the International Ultraviolet Explorer (IUE), we present a study of the properties characterizing the gas phase of the interstellar medium in the vicinity of the Sun (d < 150 pc) toward five cataclysmic variables: SS Cyg, V3885 Sgr, IX Vel, RW Sex, and AM Her. In addition to the absorption lines of the neutral and singly -ionized species in the neutral interstellar gas along the line of sight to these cataclysmic variables, we identify narrow velocity-shifted absorption lines of CIV, Si IV, and Si III in the spectrum of SS Cyg, and thereby infer the existence of an expanding H II region of interstellar gas ionized by the EUV and soft X-ray flux of this cataclysmic variable. In addition to the effect the ionizing flux of cataclysmic variables has on the interstellar medium, as evidenced by the P Cygni profiles of their ultraviolet resonance lines, cataclysmic variables experience mass loss to the interstellar medium in the form of a high-velocity wind. In order to investigate the nature of the winds of cataclysmic variables, we present an observational and theoretical study of the P Cygni profiles of these systems, giving particular attention to the profile revealed by low-resolution IUE spectra of the dwarf nova HL CMa.