Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 188-196). Available also in a digital version from Dissertation Abstracts.

We present new, accurate astrophysical parameters for both components of the six short-period Algol-type binary stars RZ Cas, AT Peg, TX UMa, AF Gem, RU UMi and HU Tau. The accuracy of the astrophysical parameters is ensured by the determination of a mass ratio for each of the systems from the spectroscopic orbits of both components via the cross correlation technique. For RZ Cas and AT Peg we have developed a simple technique to correct the observed photometry for the presence of the secondary component. Spectral classification of the primary component of AT Peg was aided by the use of an improved Doppler tomography technique. The systems RZ Cas, AT Peg, TX UMa, AF Gem and HU Tau are found to be apparently normal semi-detached Algol-type systems and accurate masses and radii have been determined with a typical precision of a few percent. For RU UMi we have been able to confirm the suspected semi-detached configuration. We have compiled a list of nine Algol-type binary stars, five from this study, for which the observed astrophysical parameters have been determined accurately using a combination of both spectroscopic and photometric data in a self-consistent solution. The general model of non-conservative case B evolution adequately explains the properties of these systems as a group. Angular momentum loss via a magnetic stellar wind is shown to be an important factor in the evolution of these systems. However, there appear to be no published evolutionary models which can be used to estimate the properties of the progenitors of these systems. For the more massive systems the best available models predict periods that are too large by ~50-250% and luminosities for the faint components that are too high by factors of 10-20.

M.Sc. / This project involves the analysis of data obtained through membership of the Kepler Asteroseismic Science Consortium Working Group 9, viz. proprietary data received from the Kepler Space Telescope. In this work, Kepler data on KIC011175495 are de-trended, and subject to a lengthy iteration of refined and sophisticated analysis routines, using many software platforms based on sound physical principles. The iteration is shown to converge to final values for the binary parameters and the pulsation frequencies present in the system. Conclusions are made on the interpretation of these results and the way forward for further analysis of this and related systems.

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Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: D.E. Winget. Vita. Includes bibliographical references. Also available from UMI.

Thesis (Ph. D.)--University of Florida, 1982. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 95-97).

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Les étoiles Miras sont des étoiles froides et évoluées (étoiles AGB), caractérisées par une variation de luminosité régulière et de longue période liée à une pulsation radiale. Cela se traduit par une atmosphère froide, étendue et faiblement liée gravitationnellement. Dans le spectre de ces étoiles, la détection variable d'émissions intenses dans les raies de Balmer de l'hydrogène est usuellement reliée à la propagation périodique d'une onde de choc radiative hypersonique dans l'atmosphère. Mon travail de thèse a eu d'abord pour objectif de confirmer l'existence d'une forte signature de polarisation linéaire accompagnant ces émissions, d'origine inconnue et déjà observée auparavant, et de caractériser son évolution temporelle. Je me base sur un suivi spectropolarimétrique inédit et effectué dans le cadre de ma thèse avec l'instrument NARVAL pour plusieurs Miras afin d'établir cette caractérisation. Ces suivis ont été réalisé sur tous les paramètres de Stokes (polarisation linéaire et circulaire) et surtout à des phases autour du maximum de luminosité.Un résultat majeur de ces observations est la détection systématique de signatures polarisées (polarisation surtout linéaire mais aussi parfois circulaire) liées aux émissions en intensité dans les raies de Balmer. L'utilisation d'un code de simulation d'atmosphère dynamique m'a permis de confirmer le lien entre une onde de choc et la présence d'émission dans ces raies, chose qui n'avait jamais été montrée par un modèle jusque là. Ces éléments me font affirmer que le mécanisme de polarisation est intrinsèque à l'onde de choc. La discussion sur l'origine de cette polarisation comporte deux grands axes : l'asymétrie globale de l'onde de choc amenant à une polarisation nette du rayonnement et la production locale dans le front du choc d'un champ magnétique responsable d'une polarisation par impact dans la zone de production des photons Balmer, c'est-à-dire le sillage du choc. D'autre part, j'invoque la possibilité d'une instabilité de Parker comme deuxième facteur de polarisation par impact et je discute le rôle potentiel de l'effet Hanle. / Mira stars are cool and evolved stars (AGB stars), characterized by a regular luminosity variation and a long period linked to a radial pulsation. All this imply a cool and extended atmosphere which is weakly linked by gravity. In the spectra of those stars, the variable detection of intense emissions in the Balmer lines of hydrogen are usually linked to the periodical propagation of a hypersonic radiative shock wave in the atmosphere. My thesis work's first objective was to confirm the existence of a strong polarimetric signature accompanying those emissions, whose origin is still unknown and already observed before, and to characterize its evolution through time. I rely on a novel spectropolarimetric survey, done in the framework of my thesis with the NARVAL instrument for several Mira stars in order to establish this characterization. Those surveys were done on all Stokes parameters (linear and circular polarization) and mainly during phases around the maximum of luminosity.A major result of these observations is the systematic detection of polarized signatures (mainly linear polarization but also circular sometimes) linked to the emissions in intensity in the Balmer lines. The use of a dynamical atmosphere simulation code allowed me to confirm the link between a shock wave and the presence of emissions in those lines. Such a result has never been been produced by a model until now. These elements make me state that the polarization mechanism is intrinsic to the shock wave. The discussion on the origin of such polarization consists of two main axes : the global asymmetry of the shock wave leading to a net polarization of the radiation and the local production in the shock's front of a magnetic field responsible for an impact polarization in the area of production of Balmer photons, namely the shock's wake. Besides that, I mention the possibility of a Parker instability as a second factor of impact polarization and I discuss the potential role of the Hanle effect.