Department Library


Liberty Rae Evanko (PhD Dissertation, March 2007, Advisor: Benjamin Taylor )


One phase of formation of medium- and low-mass stars is the optically visible phase known as the pre-main-sequence or PMS phase. In order to further the understanding of this phase, more of these PMS objects need to be identified and classified. Previous techniques have used photometry to identify possible PMS objects by their characteristic Hα emission. Once identified these objects can be studied spectroscopically yielding complete PMS classification. This study develops a method to locate these emission objects that overcomes two limitations of previous techniques. The first limitation is the need for the creation of reddening maps. It is eliminated by the creation of a reddening free Hα wide/narrow index for the selection of emission objects. The second limitation is the requirement of the creation of mosaics to study the entire region of interest. This limitation is overcome by the construction of a wide-angle observation facility. This makes it possible to obtain the entire region of interest in a single frame. Once tested to ensure the validity of the method, the wide-angle Hα wide/narrow procedure is applied to several young open clusters. The development of the index and the results of its application to the clusters are presented. Also, an examination into how the results can be used to address some of the questions currently surrounding the PMS is included. Finally, a guideline for the implementation of the method into future studies is discussed.


James E Maxwell (Masters Thesis, December 2004, Advisor: Benjamin Taylor )


Understanding the character of star clusters is an important part of astronomical research. The quality of cluster research is directly related to the quality and breadth of the methods used when deriving photometric results. For these crowded fields, point spread function (PSF) photometry id the best method available for accurate magnitudes and colors. This photometry must also be standardized in order to be of maximum use. DAOPHOT is a program that performs PSF photometry. The program BIGPHOT standardizes photometry. A new method has been developed which will take the output from DAPHOT, correct it for the zeropoint jitter inherent in PSF photometry, and the put it in a form that is suitable for use with BIGPHOT. As part of this method, several scripts were written to ease the use of BIGPHOT and the correction process. A program called BIGFRONT was also created as a front-end program for BIGPHOT. This program converts easily formatted data files to the form required by BIGPHOT. This new method will be shown to produce usable results in crowded field using M67 (NGC 2682) as a test cluster. The methods will also be demonstrated on frames for M35 (NGC 2168) and w Centauri (NGC 5139) through a presentation of color magnitude diagrams for all three clusters. This method will be documented for use by future researchers in the form of a step-by step manual.


J. Edward Maxwell (Senior Thesis, April 2003, Advisor: Benjamin Taylor )


Phillip Bernell Warner (Masters Thesis, August 2003, Advisor: Benjamin Taylor )


This thesis presents the first γ Doradus instability strip, created using the stellar modelling codes graciously provided by Joyce A. Guzik and Anthony B. Kaye of the Los Alamos National Laboratories. The instability strip was mapped for Z + 0.02, and ι∈ [1,5]. The results show that the strip overlaps the red edge of the δ Scuti instability strip, and provides for the possibility that stars showing both γ Doradus and δ Scuti modes of pulsation (i.e., hybrids”) exist. The model instability strip agrees very well with the previously-established, observationally-based, instability strip of Handler & Shobbroook (2002). As in Guzik et al. (200b), the convection zone depth plays the major role in the determination of the γ Doradus instability strip. Once this depth becomes too deep or too shallow, the convection zone no longer allows for pulsation instability. The theoretical γ Doradus instability strip is bounded by ~ 6850 – 7360K at the red and blue edge, respectively, on the zero-age main sequence and by ~ 6560 – 7000K at the red and blue edge, respectively, approximately two magnitudes more luminous. This theoretical strip, transformed to the observers color-magnitude diagram, overlays the region where most of the 30 bona fide γ Doradus stars are found.


Jacob John Albretsen (Masters Thesis, December 2002, Advisor: Benjamin Taylor )


We report on observations using the Cousins V RI photometric system. Sixty-seven standard stars used for 13 nights to determine solutions for 58 program stars. The propose for these solutions is to expand standard star data sets for the Cousins V RI system and make quantitative comparisons between photomultiplier and CCD observations. Program stars fall into the magnitude range 16.508 < V > 10.480 and in color range 0.043 < (V - R) < 1.532 and 0.074 < (R – I) < 1.575. Comparisons with photomultiplier results from Landolt [10] show a 6.4 mmag mean residual statistically for R- I, but no significant offsets for V and V – R.


Liberty Rae Evanko (Masters Thesis, December 2001, Advisor: Benjamin Taylor )


Using a variety of Baade-Wesselink solutions, improved radii have been obtained for the two dwarf Cepheids, AD Canis Minoris and EH Librae. This project contains new visual photometric, infrared photometric and radial velocity observations that were obtained both at Brigham Young University and the South African Astronomical observatory facilities. With these data, the radii were found to be 2.92 ± 0.08R and 2.58 ± 0.05 R for AD CMi and EH Lib, respectively. These values are in good agreement with previous measurements. Success and limitations of the method are discussed. The radii determined for these stars were used to further examine the use of dwarf Cepheids as “standard candles”. Much as the well-known period-luminosity relation for Cepheids, a period-radius relation would allow dwarf Cepheids to be used to obtain distances with relative ease. Continued use pf this method to obtain radii for stars in this variable class should lead to a well-defined period-radius relation for dwarf Cepheids.

Matthew Bodell Garvin (Masters Thesis, December 2001, Advisor: Benjamin Taylor )


This thesis presents my investigation into the Sivo nu-View II spectrograph and the BYU spectrograph as candidates for use at the observatories operated by the Department of Physics and Astronomy at Brigham Young University. I discuss the capabilities and limitations of each spectrograph. I focus on the efforts made to refit the BYU spectrograph with a CCD camera. I present procedures for operating and caring for the BYU spectrograph and its components. I conclude that the Sivo spectrograph is not capable of supporting as wide a range of research as the BYU spectrograph. I also conclude that the BU spectrograph is not currently capable of producing publication quality data because of a problem with the thermal stability of the CCD camera.


Kenneth A Nelson (Masters Thesis, December 1997, Advisor: Benjamin Taylor )


This thesis is a study of the Bootes Void, thought to one of the largest voids in existence. A new center and distance for the Void are proposed, and the question of the Void’s degree of emptiness is addressed. A series of Wolf Diagrams is presented, depicting fifteen areas along δ=43.5° and running from α=13h40m to α=15h04m. The slopes of these plots are interpreted and compared to Wolf Diagrams of various model distributions. A discussion of the analysis methods used is also included.


Scott B Johnson (Masters Thesis, August 1987, Advisor: Benjamin Taylor )


Observations 314 stars with the uyby-beta photometric system are used to establish the reddening in the direction of the nearby Triangulum galaxy, M33. Color excesses are obtained for 151 A- and F-type stars in a one degree radius centered around the galaxy. A color excess of E(b-y) = Om.057 (E(B-V) = 0m.077) is obtained for a distance modulus m-M = 10. A secondary result of this investigation is the discovery of six suspected variable stars as well as ten observations of V Triangulum, a beta Lyrae-eclipsing variable.