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 17 of 17 for “"Circumstellar disks"”.
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Dust in circumstellar disks
… and spatial distribution of dust particles in circumstellar disks. Using millimetre interferometric observations of optically thick disks around T Tauri stars, I provide conclusive evidence for the presence of millimetre- to centimetre-sized dust aggregates. These findings demonstrate that dust …
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A New Era of Observational Capability at Ritter Observatory: Spectropolarimetry from Exoplanets to Circumstellar Disks and Beyond
We undertook efforts to restore and relocate the University of Wisconsin's Halfwave-Polarimeter (HPOL) spectropolarimeter to the University of Toledo's Ritter Observatory. This process required fairly extensive work to the optical-mechanical alignment of the Ritter Observatory 1-meter telescope. …
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Accretion disks in the cataclysmic variables
… the time-independent structure of gaseous circumstellar disks in vertical hydrostatic equilibrium are derived. The possibility of turbulent instablilty and the resulting viscosity laws are discussed.
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High-resolution studies of protoplanetary disks
… (near-IR, mid-IR, mm) for previously unknown circumstellar disks and a study of those disk candidate objects which are not yet well characterised in the literature. 22 candidate stars, most of these constituting known exoplanet systems, were examined for circumstellar material using the …
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Coronagraphic data post-processing using projections on instrumental modes
… exoplanets and a multitude of brown dwarfs and circumstellar disks. Despite advances in coronagraphy and wavefront control, high contrast observations are still plagued by residual wavefront aberrations. Post-processing techniques can provide an additional boost in separating residual …
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Spectroscopic and spectro-astrometric analysis of T Tauri Stars
… low-mass, pre-main sequence stars surrounded by circumstellar disks of material from which planets are believed to form. We present high-resolution, near-infrared spectroscopic data for the T Tauri stars DR Tau and AA Tau using NIRSPEC at the Keck II telescope. For DR Tau, a spectro-astrometric …
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Circumstellar Structure Properties of Young Stellar Objects: Envelopes, Bipolar Outflows, and Disks
… objects (YSOs), envelopes, bipolar outflows, and circumstellar disks, have been studied using radio interferometers: the Berkeley-Illinois-Maryland Association (BIMA) array and the Combined Array for Research in Millimeter-wave Astronomy (CARMA). (1) Envelopes: Three Class 0 YSOs (L1448 IRS 2, …
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Exploring the Environment of Young Stars: Disks, Companions and Clusters
… NACO/VLT instrument we probe one of the closest circumstellar disks in the planet-forming age at scales of our inner Solar System. 2. Our adaptive optics survey discovers six companion candidates to young stars. The most interesting one is close to the well-known outburst star FU Ori and is a …
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Observations of disks around the youngest protostars: Characterizing frequency, dust properties, and magnetic fields at the earliest times
Circumstellar disks are fundamental for accretion and angular momentum distribution during the early phases of star formation. Class 0 objects are the youngest protostars and most embedded in their natal envelopes, and circumstellar disks can form even at this earliest stage of star formation. …
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Describing protostellar disk structure in Ophiuchus
Young forming stars host circumstellar disks of dust and gas. High-resolution, millimeter observations of disks at the protoplanetary stage reveal substructures such as gaps, rings, arcs, spirals, and cavities. These structures are often attributed to disturbances from young, newly formed planets …
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Mass Functions and Mass Segregation in Young Starburst Clusters
… Halpha data, both serving as tracers for circumstellar disks. Disk survival in starburst clusters is discussed. The present-day mass function (MF) of both clusters is deduced from colour-magnitude diagrams. Radial variations in the MFs reveal a heavily mass-segregated core in both …
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High resolution studies of early type emission line stars
… angles are compared to a model in which the circumstellar disk and binary orbits are co-planar. The data are consistent with the coplanar model and thus with the scenario of disk fragmentation. A search for optical outflows associated with Herbig Ae/Be stars is conducted using integral field …
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Planetary Systems in Polarized Light: Debris Disk Observations and Instrumentation
… observations can be useful for imaging debris disks and characterizing exoplanet atmospheres. With that in mind, this thesis has been constructed with two main aspects: i) observational studies of two debris disk systems, Beta Pic and HD 157587, using the Gemini Planet Imager and ii) the …
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Probing planetary system histories via observations, experiments, and modelling of circumstellar gas and dust
Circumstellar disks of gas and dust are integral parts of planetary systems from formation to maturation. Protoplanetary disks, the name for circumstellar material at the earliest stages of a stellar lifetime, provide key information about the formation processes of planets, and therefore of the …
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The Inner Gaseous Disks Of Herbig Be Stars
… 20Msun) pre-main sequence stars that inherit a circumstellar disk of dust and gas from their formation phase. The region of this disk closest to the star is entirely gaseous because dust evaporates at the high temperatures there, and this gaseous region is currently poorly understood. Using …
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The Structure of Extrasolar Planetesimal Belts in Images
… that population this region, known as debris disks. As planets dynamically interact with the disk throughout their formation and evolution, structures reflecting their history are imprinted on the disk. In this thesis, I develop systematic and unbiased methods to recover the three-dimensional …