Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 56 for “"White dwarf."”.
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Observational Insights into White Dwarf Planetary Systems
… their characterisation. Spectroscopic studies of white dwarfs ‘polluted’ by planetary material are a unique laboratory allowing measurements of their bulk composition. This thesis focuses on these polluted white dwarfs to observationally investigate how the material ultimately accretes onto the …
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The gravity oscillations of white dwarf stars
… numerical investigation of the oscillations of white dwarfs which is discussed below was begun at the suggestion of Professor Warner soon after the discovery of periodic variations in several cataclysmic variables. Its completion within a reasonable time was greatly helped by the availability of …
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Spectroscopy of white dwarf stars observed by HETDEX.
Approximately 97% of all stars will become white dwarf stars at the end of their life cycles, making them excellent benchmarks for testing theories of stellar evolution. For the purposes of numerical modelling, they can be treated as simple objects composed of two structures that can be treated …
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The behavior of hydrogen and helium at white dwarf photosphere conditions
White Dwarfs (WDs) represent the evolutionary endpoint for nearly all stars in the universe. Their atmospheres are usually dominated by either hydrogen, helium, or carbon. In astrophysics, WDs are used to determine the age of the universe, to test current stellar evolutionary models, and to …
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Population boundaries and gravitational-wave templates for evolving white dwarf binaries
We present results from our analysis of double white dwarf (DWD) binary star systems in the inspiraling and mass-transfer stages of their evolution. Theoretical constraints on the properties of the white dwarf stars allow us to map out the DWD trajectories in the gravitational-wave …
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Pulsations in the white dwarf primary of a cataclysmic variable star
… powerful techniques for the study of pulsating white dwarf stars. If these techniques could be applied to the white dwarf primaries of Cataclysmic Variable stars, the study of accretion in interacting binary systems would benefit enormously. Our understanding of normal modes in white dwarf …
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The element distribution of cosmic rays produced by white dwarf spinars.
Thesis: B.S., Massachusetts Institute of Technology, Department of Physics, 1972
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Characterization of the Galactic White Dwarf Population in the Next Generation Virgo Cluster Survey
Halo white dwarfs remain one of the least studied stellar populations in the Milky Way because of their faint luminosities. Recent work has uncovered a population of hot white dwarfs which are thought to be remnants of low-mass Population II stars. This thesis uses optical data from the Next …
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Theoretical statistics of zero-age cataclysmic variables
"The distribution of the white dwarf masses, the distribution of the mass ratios and the distribution of the orbital periods in cataclysmic variables which are forming at the present time are calculated. These systems are referred to as ""zero-age cataclysmic variables"". The results show that 60% …
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ΣΥΜΒΟΛΗ ΣΤΟ ΠΡΟΒΛΗΜΑ ΤΗΣ ΔΙΑΦΟΡΙΚΗΣ ΠΕΡΙΣΤΡΟΦΗΣ ΕΝΟΣ ΛΕΥΚΟΥ ΝΑΝΟΥ ΜΕ ΑΝΑΠΤΥΞΗ ΚΑΙ ΕΦΑΡΜΟΓΗ ΘΕΩΡΙΩΝ ΔΙΑΤΑΡΑΧΗΣ
… DEGENERATE ELECTRON GAS CONTINUUM, FORMING A WHITE DWAR. THE AIM OF CHAPTER 1 IS TO SPECIFY THE STRUCTURE DIFFERENTIALLY ROTATING WHITE DWARF BY EXTENDING CHANDRASEKHAR'S METHOD TO INCLUDE UP TO THIRD ORDER TERMS IN THE ROTATIONAL PERTURBATION PARAMETER. IN CHAPTERS II AND III WE OBTAIN …
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Polluted White Dwarfs: Insights into Ancient Extrasolar Planetary Systems
… this thesis, I demonstrate how the pollution of white dwarf stars by rocky exoplanetary material offers an insight into the bulk composition of rocky exo-planets, and thus, the geological processes which occur on them. I present a model which reproduces the atmospheric metal abundances present in …
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Gravitational Wave prediction from Galactic binary populations for LISA
Galactic binaries, such as white dwarf binaries and black hole binaries, are expected to be the primary sources of gravitational waves (GWs) detectable by the Laser Interferometer Space Antenna (LISA). Detecting these sources provides an opportunity to unravel critical details about binary star …
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Accretion topics in astrophysics
… The third work studies the tidal stripping of a white dwarf spiraling into a massive black hole. The stripped matter accretes onto the black hole producing a transient emission, presumably periodic, observable with X-ray and optical telescopes. At the same time the white dwarf emits gravitational …
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Gravitational Lensing in the Solar Neighbourhood and Towards the Milky Way Bulge
… microlensing event where the lens is a nearby white dwarf. Analysis of this event permitted a direct mass determination of the white dwarf which in turn allowed a test of the white dwarf mass-radius relationship. In Chapter 4, I present a search for predicted photometric microlensing events. …
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Characterisation of the Components in Cataclysmic Variables
… visible. It concentrates on the eclipsing dwarf nova OY Carinae, which has been observed both in superoutburst and quiescence. Optical 'wide B' band light curves were obtained at the end of the 1994 superoutburst and on the decline. Eclipse mapping of these light curves reveals an accretion …
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Accretion processes in cataclysmic variable stars: insights from optical transient surveys
… accretion from a main sequence donor star to a white dwarf star. Multiple CV subclasses exist with varia tions in the nature of the CV, many of which have accretion discs surrounding the accretor. This study focuses on two sub-classes of CVs, namely AM Canum Venaticorum (AM CVn) stars with …
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Cool white dwarfs and the age of the galaxy
White dwarf stars represent the most common endpoint of stellar evolution and therefore provide a reliable estimate of the star formation history and age of different Galactic populations. The major observational requirement for accurate age measurements is to have a large sample of cool, old white …
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Multi-dimensional Monte Carlo radiative transfer simulations: investigating the double detonation scenario for type Ia supernovae
… have shown that sub-Chandrasekhar mass white dwarfs are promising candidates for the progenitors of SNe Ia, and can reproduce a number of the observed features of SNe Ia. The ‘double detonation’ explosion mechanism is a widely discussed scenario by which an explosion in a …
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The binary system containing the pulsar PSR 1913+16 and ultra-violet and x-radiation from accreting magnetic white dwarfs
… the companion be a black hole, a neutron star, a white dwarf or a helium main-sequence star. Observable second-order relativistic effects mayor may not further restrict the list of candidates. The discussion summarjzes Masters and Roberts, 1975 Ap. J. (Letters), l.25.., L 107, and Roberts t …
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Multiwavelength studies of classical novae
… from an eruption on the surface of an accreting white dwarf in interacting binary stars, namely cataclysmic variables. These eruptions and their progenitors are ideal astronomical events/objects to study a variety of interesting topics, such as mass-transfer mechanisms, binary evolution, and …
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