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Parsons, S. G. (2012) Eclipsing white dwarf binaries. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b2582736~S1
Abstract
Recent years have seen an explosion in the number of eclipsing binaries containing
white dwarfs. In the last few years the number of systems has increased from 7
to over 40, thanks mainly to large surveys such as the Sloan Digital Sky Survey
and the Catalina Sky Survey. Many of these systems are survivors of the common
envelope phase during which the two stars orbit within a single envelope which
is rapidly thrown off through loss of energy and angular momentum. Detailed
analysis of these systems can yield extremely precise physical parameters for both
the white dwarf primary and its companion star. Stellar masses and radii are some
of the most fundamental parameters in astronomy and can be used to test models of
stellar structure and evolution. They can also be used to constrain the evolutionary
history of the binary system offering us the chance to better understand the common
envelope phase itself.
In this thesis I present high-precision studies of several eclipsing post common
envelope binaries. I use a combination of high-speed photometry and high-resolution
spectroscopy to measure the masses and radii of both stars in each system. I compare
these results to evolutionary models and theoretical mass-radius relations and find
that, on the whole, the measured masses and radii agree well with models. However,
the main-sequence companion stars are generally oversized compared to evolutionary
models, although this deviation is much less severe at very low masses (<
∼ 0.1M⊙). I
also find that the measured masses and radii of carbon-oxygen core white dwarfs are
in excellent agreement with theoretical models. Conversely, the first ever precision
mass-radius measurement of a low-mass helium core white dwarf appears undersized
compared to models.
Large scale surveys have also begun to identify double white dwarf eclipsing
binaries. In this thesis I present a study of one of these systems and show the
potential, as a double-lined spectroscopic binary, of measuring precise parameters
for both stars in the future.
Finally, I show that the mid-eclipse times of eclipsing binaries containing
white dwarfs can be measured to a high enough precision that we can monitor them
for evidence of period changes. I find that many systems show complex variations
in their eclipse times and in many cases the only mechanism able to produce these
changes is one or more sub-stellar objects in orbit around the binary. However, I
show that care must be taken when attempting to detect planets in binary systems
using eclipse timings.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QB Astronomy | ||||
Library of Congress Subject Headings (LCSH): | Eclipsing binaries, White dwarf stars | ||||
Official Date: | January 2012 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Department of Physics | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Marsh, T. R. | ||||
Extent: | xiii, 187 leaves : ill., charts | ||||
Language: | eng |
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