Thesis (M. Phil)--University of Queensland, 2004. / Includes bibliographical references.

Thesis (Ph. D.)--Georgia State University, 2005. / Theo A. ten Brummelaar, committee chair; Brian D. Thoms, Todd J. Henry, William G. Bagnuolo, Douglas R. Gies, Harold A. McAlister, committee members. Author's name from thesis t.p. Electronic text (548 p. : ill.) : digital, PDF file. Description based on contents viewed June 27, 2007; title from title screen. Includes bibliographical references (p. 539-548).

No description available.

No description available.

No description available.

No description available.

No description available.

This dissertation describes the techniques involved in using a fiber optic coupled spectrometer to do multiple object spectroscopy of astronomical objects. The Medusa spectrograph, with optical fibers fixed in a focal plane aperture plate, was used to study clusters of galaxies via velocity distributions. Some relevant problems in the study of the structure and dynamics of clusters of galaxies are outlined as motivation for building a multiple fiber spectrometer. The history of fiber optic spectroscopy in astronomy is presented along with an outlook for the future. The results and experience gained from the Medusa spectrograph are used to design a second generation instrument. The MX Spectrometer uses optical fibers which are positioned remotely under computer control. These fibers are optically matched to the telescope and spectrograph optics to achieve optimum performance. The transmission, flexibility, and image scrambling properties of step-index silica fibers allow efficient reformatting of multiple objects into the spectrometer entrance aperature. By allowing spectra of 32 objects to be obtained simultaneously, the MX Spectrometer will make an order of magnitude increase in the quantity of spectroscopic data that can be recorded with a large telescope. Mechanical, control, and optical elements of the MX design are discussed. Telescope and fiber parameters influencing the design of the fishermen-around-the-pond mobile fiber head are detailed. Results of testing the stepper motor driven fiber positioner probes are described. The algorithm for controlling the motion of 32 positioners in the telescope focal plane without collisions is outlined. Detector performance and spectrometer efficiency are considered for both the Medusa and MX systems. The use of a Charge Coupled Device (CCD) array detector provides increased quantum efficiency, dynamic range, and stability, as well as allowing digital sky subtraction. Microlenses and their use in correctly coupling optical fibers to the telescope and spectrograph are discussed. In particular, the pupil-imaging technique for microlens matching to fibers is introduced.

The magnetic rotator model has long been the favored explanation for coherent photometric modulations in the DQ Herculis class of cataclysmic variables. However, to date, all evidence supporting this model has been of the indirect variety. Unlike their synchronously rotating cousins, the AM Herculis objects, DQ Herculis stars have not yet been discovered to emit polarized radiation. Therefore, in light of this crucial lack, the evidence used to place these objects in the magnetic cataclysmic variable category has been strictly circumstantial, based primarily on the coherence of the photometric periodicities. In this work, time-resolved spectroscopy of four long-period DQ Herculis stars is performed. In addition, two of the same objects are observed with a new, sensitive circular polarimeter. Chapters II and III describe these observations and the results of each. To summarize, coherent variations in the wavelength of emission lines were found with the spectroscopic observations. A model is put forth, explaining this phenomenon as being due to varying illumination from a bright spot on the primary. This, of course, adds strength to the magnetic rotator model. Secondly, circular polarization was definitely found in one object studied, and possibly in a second. Therefore, for the first time, there is direct evidence of the magnetic nature of these binaries. In Chapter IV, the model of the rotating bright spot illuminating the disk is explored in further detail, including modeling with a minicomputer. Afterward, a problem brought out by the low polarization coupled with large amplitude photometric variations and a cool spectrum is investigated, namely, is it possible to produce large amounts of cyclotron radiation without producing large amounts of circular polarization? The results tend to show that, for a large emitting area, the answer is yes. Chapter V is a summary of the rest of the work.

"August 2001." Includes bibliographical references (p. 308-311). Describes the use of optical telescopes in the investigation of astronomical objects which have been discovered by earth-orbiting high-energy astronomical satellites.