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 30 for “"Binary stars"”.
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Computational starspot photometry of contact binary stars
Starspots are not well understood for contact binary star systems. The following properties of spots were systematically investigated: temperature, radius, colatitude, and longitude. Spots were modeled on an AE Phe like contact binary system. The spots were changed in a systematic manner. The light …
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Be binary stars with hot, compact companions
In this study the importance of close binary evolution for Be star formation was investigated. The Be star 59 Cygni was confirmed to be an evolved binary with a sdO companion. The companion was confirmed by a weak helium II absorption. Orbital elements and stellar masses were determined. In the …
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An Investigation of Rotational Velocities in Close Visual Binary Stars
Made available in DSpace on 2014-12-10T23:45:12Z (GMT). No. of bitstreams: 1 7310082.pdf: 2068610 bytes, checksum: fb4bc05ba4a6ca07435f795d3a580c63 (MD5) Previous issue date: 1972
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Searching for Ultra-compact binary stars with the MeerLICHT Southern All-Sky Survey
… population of AM Canum Venaticorum (AM CVn) stars, a rare type of ultra-compact binary star. This was done by searching through the MeerLICHT Southern All-Sky Survey (ML SASS) data with a candidate selection process which made use of a selection technique based on the colours of stars. The …
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Rites of Offering: Stability, Outcomes, and Observational Signatures of Mass Transfer in Binary Stars
Contains fulltext : 332404.pdf (Publisher’s version ) (Closed access)
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The role of binary stars in searches for extrasolar planets by microlensing and astrometry
When Galactic microlensing events of stars are observed, one usually measures a symmetric light curve corresponding to a single lens, or an asymmetric light curve, often with caustic crossings, in the case of a binary lens system. In principle, the fraction of binary stars at a certain separation …
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Processing of Simulated and Experimental Images of Closely Spaced Binary Stars Using Speckle Interferometry
… speckle interferometry data from close visual binary stars are presented and implemented. The effects of the optical systems used for observing close visual binary stars are explained and simulated from both the geometrical and physical optical viewpoints. The atmospheric phase distortion and …
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A catalog of new eclipsing binaries in the Kepler database
In this thesis, we present a catalog of binary stars discovered in the publicly available Kepler database, none of which were included in previous such catalogs published by the Kepler science team. A brief review of other binary star catalogs is given, including the Prs̆a et al. catalog on which …
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A Feasibility Study for Using the ERAU Échelle Spectrograph to Improve Orbital Parameters of Spectroscopic Binary Systems
<p>Binary stars are critical for establishing knowledge of stellar masses and refining the mass-luminosity relationship when used in conjunction with precise parallax measurements. However, many spectroscopic binaries have poorly defined orbital parameters as they have not been revisited with newer …
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Binary star systems and extrasolar planets
For ten years, planets around stars similar to the Sun have been discovered, confirmed, and their properties studied. Planets have been found in a variety of environments previously thought impossible. The results have revolutionized the way in which scientists understand planet and star formation …
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Rapid mass transfer in binary systems
… the conditions for rapid mass transfer in binary stars. Previous theoretical calculations and observations of binaries imply the existence of several different timescales for mass transfer: nuclear, thermal, or dynamical. Since the mass transfer rates differ by several orders of magnitude, …
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Monte-Carlo simulations of globular cluster dynamics
… cluster evolution using a realistic number of stars (N - 10 - 106) and taking into account the full range of relevant stellar dynamical and stellar evolutionary processes. These processes include two-body gravitational scattering, strong interactions and physical collisions involving both …
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Ambipolar Diffusion in Interstellar Clouds: One-Dimensional, Isothermal Collapse
… the angular momentum problem (at least for binary stars and, most likely, for single stars as well) during the early, relatively diffuse stages of cloud contraction. The magnetic flux problem lies in the observation that fluxes of typical stars are between 2 and 5 orders of magnitude smaller …
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Accretion processes in cataclysmic variable stars: insights from optical transient surveys
Cataclysmic variable (CV) stars are binary stars mostly characterised by 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 …
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Optical and gamma-ray study of gamma-ray binaries
Gamma-ray binary stars are intriguing interacting stellar systems that exhibit emission across the whole electromagnetic spectrum. This thesis is focused on optical and gamma-ray emission of gamma-ray binary stars (GRBis). I have performed radial velocity measurements of 1FGL J1018.6-5856 to derive …
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Exploring the Environment of Young Stars: Disks, Companions and Clusters
… FU Ori phenomenon and the formation of massive stars. The main results are the following: 1. By applying the novel method of polarimetric differential imaging and the NACO/VLT instrument we probe one of the closest circumstellar disks in the planet-forming age at scales of our inner Solar …
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Refinements and improvements to a phenomenological model for the jet opening angles of gamma-ray bursts
… the core collapse of massive, rapidly rotating stars - events called "hypernovae." In this thesis, we improve upon a phenomenological model to determine [theta], the jet opening angle of GRBs. We assume that hypernova progenitors are massive stars in binary systems. We calculate [theta] by …
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Solving the N-body problem in astrophysics
… (planets with moons, planetary systems with binary stars, etc.), the integrators are far more efficient than alternatives. I show numerically that a popular code is neither symplectic nor time-symmetric, and can yield incorrect three-body dynamics. I derive symplectic integrators in various …
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Merging neutron star and black hole binaries: Inference of their parameters and simulations of their formation and fate
… (i) We present measurements of properties of the binary neutron star and black hole observations from the LIGO-Virgo observatories' second observing run, using Bayesian parameter estimation on the gravitational-wave data. During this observing run, LIGO-Virgo for the first time reported …
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Rotation and magnetism in massive stars
… number of important effects on the evolution of stars. Apart from structural changes because of the centrifugal force, turbulent mixing and meridional circulation can dramatically affect a star's chemical evolution. This leads to changes in the surface temperature and luminosity as well as …
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