Fundamental Properties of White Dwarfs Alone and In Binaries
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Fuchs, Joshua. Fundamental Properties of White Dwarfs Alone and In Binaries. 2017. https://doi.org/10.17615/bacp-4370APA
Fuchs, J. (2017). Fundamental Properties of White Dwarfs Alone and In Binaries. https://doi.org/10.17615/bacp-4370Chicago
Fuchs, Joshua. 2017. Fundamental Properties of White Dwarfs Alone and In Binaries. https://doi.org/10.17615/bacp-4370- Last Modified
- March 20, 2019
- Creator
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Fuchs, Joshua
- Affiliation: College of Arts and Sciences, Department of Physics and Astronomy
- Abstract
- White dwarfs are physically simple and numerous. Their properties provide insight into stellar evolution and have applications to many astrophysical questions. In this dissertation, we present new measurements of white dwarf properties in two environments that help further our knowledge of the structure and evolution of white dwarfs. We have undertaken a series of observations that enable the measurement of fundamental parameters of the white dwarf in two magnetic cataclysmic variables. We have chosen these particular systems because the lack of accretion disk and fortunate geometry leading to eclipses makes it possible to observe and characterize the white dwarf. In one system, we confirm that LSQ1725-64 is a magnetic cataclysmic variable by estimating the magnetic field strength of the white dwarf from Zeeman splitting. We measure the effective temperature of the white dwarf and the spectral type of the secondary star from spectroscopy during a state of low accretion. Our precise eclipse measurements allow us to estimate the white dwarf mass and other binary parameters of LSQ1725-64. The spectral type and color of the secondary, as well as the eclipse length, are consistent with other secondaries that have not yet evolved through the period minimum expected for cataclysmic variables. In CTCV1928-50, we detect H alpha emission from the heated face of the secondary that we use to measure the radial velocity amplitude of the secondary star. We combine this with previous measurements to estimate a white dwarf mass and other binary parameters. Our measurements in these two systems add to a limited number of measured white dwarf parameters in magnetic cataclysmic variables. We have also completed a spectroscopic survey of pulsating, hydrogen-dominated atmosphere white dwarfs. These pulsations have long offered the promise to conduct seismology of white dwarfs to understand their internal structure and composition. We have spectroscopically observed 122 DA white dwarfs that are either pulsating or close to the DA instability strip. We estimate Teff and log(g) for each white dwarf from the shape of the Balmer line profiles. These parameters provide important initial constraints for both absolute and relative seismology. We have completed a careful study of ten systematics involved in the determination of Teff and log(g). Understanding and limiting these systematics has permitted us to obtain the most systematically consistent set of atmospheric parameters ever determined. This work will feed efforts to study and understand pulsating white dwarfs as a whole class instead of individually.
- Date of publication
- May 2017
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- Rights statement
- In Copyright
- Advisor
- Champagne, Arthur
- Clemens, James
- Law, Nicholas
- Townsley, Dean
- Reichart, Daniel
- Degree
- Doctor of Philosophy
- Degree granting institution
- University of North Carolina at Chapel Hill Graduate School
- Graduation year
- 2017
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