Date of Award

12-15-2016

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics and Astronomy

First Advisor

Douglas R. Gies

Second Advisor

Todd J. Henry

Third Advisor

Harold A. McAlister

Fourth Advisor

Guillermo Torres

Fifth Advisor

Russel J. White

Sixth Advisor

Joshua S. Von Korff

Abstract

Accurate knowledge of stellar parameters such as mass, radius, effective temperature, and composition inform our understanding of stellar evolution and constrain theoretical models. Binaries and, in particular, eclipsing binaries make it possible to measure directly these parameters without reliance on models or scaling relations. In this dissertation we derive fundamental parameters of stars in close binary systems with and without (detected) tertiary companions to test and inform theories of stellar and binary evolution. A subsample of 41 detached and semi-detached short-period eclipsing binaries observed by NASA’s Kepler mission and analyzed for eclipse timing variations form the basis of our sample. Radial velocities and spectroscopic orbits for these systems are derived from moderate resolution optical spectra and used to determine individual masses for 34 double-lined spectroscopic binaries, five of which have detected tertiaries. The resulting mass ratio M2/M1 distribution is bimodal, dominated by binaries with like-mass pairs and semi-detached classical Algol systems that have undergone mass transfer. A more detailed analysis of KIC 5738698, a detached binary consisting of two F-type main sequence stars with an orbital period of 4.8 days, uses the derived radial velocities to reconstruct the primary and secondary component spectra via Doppler tomography and derive atmospheric parameters for both stars. These parameters are then combined with Kepler photometry to obtain accurate masses and radii through light curve and radial velocity fitting with the binary modeling software ELC. A similar analysis is performed for KOI-81, a rapidly-rotating B-type star orbited by a low-mass white dwarf, using UV spectroscopy to identify the hot companion and determine masses and temperatures of both components. Well defined stellar parameters for KOI-81 and the other close binary systems examined in this dissertation enable detailed analyses of the physical attributes of systems in different evolutionary stages, providing important constraints for the formation and evolution of close binary systems.

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