Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Bibliography: leaves 143-144.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Supervisor: Daniel T. Jaffe. Vita. Includes bibliographical references.

Volume-limited samples indicate that red dwarfs are the most abundant stars in the Milky Way and account for most of its mass, despite their low individual masses. However, because of their low luminosity, they are extremely underdetected in magnitude-limited surveys. Complicating the task of identification is the fact that they have the same temperature as red giants and thus are in the same spectral class. We must therefore look for certain spectral features to differentiate between dwarfs and giants. Intermediate-to-broad-band photometry is one method that allows us to perform this task quantitatively. The 2MASS point source catalog contains data for -0.5 billion objects, including photometry in three broadband infrared filters. This paper discusses the manner in which these data can be analyzed to find red dwarfs and the success rate of such analysis. / Department of Physics and Astronomy

A new type of astronomical polarimeter is presented that incorporates a fused silica stress-birefringent modulator which simultaneously allows the selection of chopping frequency (≤ 5 Hz) and spectral tuning (1 ≤ λ ≤ 2.5 μm) with very high modulation efficiency. Two integrating detector packages are discussed. The first uses a single germanium photodiode and HR polaroid analyzer and achieves σᵥ = 1% for a J = 14.5 object in 0.5 hr with the MMT. The second package uses a 12 x 30 pixel HgCdTe array and MgF₂ Wollaston prism to provide four simultaneous polarimetric channels that properly eliminate the systematic errors resulting from "staring" mode operation. The instrumental polarizations of the MMT are calculated using Mueller calculus and experimentally verified. It is found that the hexagonal symmetry of the telescope cancels the large amplitude spurious polarizations that arise from the single "arms" and results in a polarimetric efficiency term that is a function only of spectral bandpass and not sky position. Therefore, the MMT behaves essentially like a clean Cassegrain telescope. The continuum polarizations of five isolated highly magnetic white dwarfs are investigated both observationally and theoretically. The most complete broad-band polarimetric survey throughout the spectral region 0.35 ≤ λ ≤ 1.65 μm is performed. An apparent correlation in the linear polarizations of Grw + 70°8247, GD229, and G240-72 is discovered. In addition, no evidence for time-dependent rotation of position angle is found for any of the stars. Hydrogen Balmer photoionization occurring from the magnetically-perturbed bound states into the Coulomb-Lorentz mixed quasi-Landau continuum is investigated with the aid of recent high field calculations. Finally, the continuum polarization of Grw + 70°8247 is compared to models for cyclotron and inverse magnetobremsstrahlung absorptions in a dipolar field. The conclusion is that the continuum polarizations of these objects still eludes an exact description. New observations of BG C Mi reveal the first definitive discovery of polarized cyclotron emission in any intermediate polar and confirms that the long-held basic model of a magnetically accreting white dwarf is correct. The wavelength dependence of circular polarization is found to increase rapidly into the near-infrared, from V(I) = -0.25±0.06% to V(J) = -1.74±0.26% and suggests a field strength in the cyclotron emission region near 5-10 MG if the system scales directly with the AM Her stars.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (M.S.)--University of Delaware, 2006. / Principal faculty advisor: John E. Gizis, Dept. of Physics & Astronomy. Includes bibliographical references.

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.

Thesis (M. Sc.)--York University, 1997. Graduate Programme in Physics and Astronomy. / Typescript. Includes bibliographical references (leaves 121-128). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL:http://wwwlib.umi.com/cr/yorku/fullcit?pMQ27361.

Not available / text

This thesis examines the structure and heating requirements of the outer atmospheres (the lower transition region, upper transition region and corona) of the five dwarfs χ¹ Ori (G0V), ϵ Eri (K2V), ξ Boo A (G8V), α Cen A (G2V) and α Cen B (K0V), and the sub-giant Procyon (F5 IV-V). Alternative fits to X-ray spectra of ten late-type dwarfs from ROSAT are made using the latest available versions of the radiative power loss codes of Raymond and Smith, Landini and Monsignori Fossi, and Mewe et al. Differences between these codes are found to arise from the choice of atomic physics and the number of transitions included. The resulting coronal temperatures and emission measures are found to follow correlations proposed by Montesinos and Jordan (1993). The lower transition region is modelled using observations made with the International Ultraviolet Explorer and up-to-date atomic data. Models of the upper transition region and corona are derived assuming a balance between the radiative and conductive losses. Wave pressure is included in these models for the first time. Recent observations with the Extreme Ultraviolet Explorer aid the choice of starting parameters. The calculations are carried out in plane parallel and spherically symmetric geometries. The models of the lower and upper transition region are then combined; the spherically symmetric models of the upper transition region fit more smoothly on to those of the lower transition region than do the plane parallel models. The new model of Procyon and new measurements of N_e resolve a previous discrepancy which led to suggestions that emission in the transition region is restricted in area. The heating requirements are examined. In the five dwarfs, but not in Procyon, the conductive fluxes at the base of the upper transition region are found to exceed the radiative energy losses for the layers immediately below. In Procyon, it is shown that acoustic wave heating is a viable mechanism for heating the lower transition region and corona, while the correlation of coronal properties with the dynamo Rossby number suggest that magnetic heating models are more likely for the five dwarfs.