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 14 of 14 for “"stellar atmospheres"”.
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Effects of convection and non-equilibrium radiation transfer in stellar atmospheres /
… lines of different chemical elements in the atmospheres of different metallicity main sequence turn-off (MSTO) and red giant branch (RGB) stars. The influence of convection is assessed by analyzing differences in the elemental abundances obtained by using 3D hydrodynamical and 1D hydrostatic …
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High resolution linear spectropolarimetry: a study of the potentiality in probing stellar atmospheres and circumstellar environments
… about their basic causes. In particular, in a stellar context high resolution spectropolarimetry can potentially: (i) investigate the physics of the shaping mechanisms of the protoplanetary nebulae (PNe) and the possible interaction between the central star and the very close surrounding, (ii) …
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Generation and propagation of longitudinal tube waves in late-type stellar atmospheres and the rotation-emission activity relation
… rise. A new picture of the heating of stellar chromospheres is presented. The chromospheric emission can be explained by an ordered sequence of different heating processes which systematically vary as a function of height in the star and with its rotation rate. The low chromosphere is …
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The solar corona: modeled, discretized, visualized
In this dissertation, stellar atmospheres will be mathematically described together with the establishment of a discrete model for simulation purposes. Simulation of stellar atmospheres, such as that of our own sun, is a common task in CGI for scientific visualization, movies and games. A fibrous …
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The behavior of hydrogen and helium at white dwarf photosphere conditions
… 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 constrain the physics of Type Ia supernovae as well as …
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Modelling interstellar extinction in stellar populations
In stellar astrophysics, the determination of the magnitude of interstellar extinction is critical, due to its effect on the observed brightness and colour of the stars. Extinction is therefore an important factor in deriving scientific information from the colour-magnitude diagrams (CMDs) of …
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Non-LTE diagnostics of the infrared observations of the planetary atmosphere
… Lambda Iteration (ALI) technique developed in stellar astrophysics for spectrum formation calculations and for the computation of non-LTE model stellar atmospheres. This new for atmospheric science technique is not subject to the limitations of the traditional matrix and conventional lambda …
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Multiband Observations of Recurrent Novae
… is not helium rich. The fitting of model stellar atmospheres to observations of U Sco in quiescence, obtained ∼18-30 months after the 2010 outburst, constrains the effective temperature of the companion and indicates that it is a cool F or hot G star. The accretion disc is found to be …
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Massive stars in the Galactic Center Quintuplet cluster
… nitrogen sequence to determine their fundamental stellar parameters, and discusses the obtained results in a general context. The Quintuplet cluster was discovered in one of the first infrared surveys of the Galactic center region (Okuda et al. 1987, 1989) and was observed for this project with …
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Chemical gradients in the Milky Way from unsupervised chemical abundances measurements of the RAVE spectroscopic data set
… spectral analysis. Then, we improved the RAVE stellar parameters by modifying the RAVE pipeline and the spectral library the pipeline rely on. The modifications removed some systematic errors in stellar parameters discovered during this work. To obtain chemical abundances, we developed two …
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Molecular Spectroscopy: A Study of Molecules in Earth and Planetary Atmospheres
… AlF and AlCl have been detected in circumstellar envelopes and are predicted to occur in cool stellar and sub-stellar atmospheres.</p> <p>A new line list for the A<sup>2</sup>Σ+X<sup>2</sup>Π electronic transition of OH has been calculated. Line positions have been taken from the …
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Time Series Analysis of the A0 Supergiant HR 1040
… supergiants, HR 1040 has a highly variable stellar wind including High Velocity Absorption (HVA) events. The star was found to have an active phase with large variation in the physical characteristics of the windand with the potential for HVAs. During the active phase, correlation between …
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Hydrogen-deficient central stars of planetary nebulae
… phase of their evolution. Such fluorescent circumstellar gas is called a "Planetary Nebula". About one-tenth of the Galactic central stars are hydrogen-deficient. Generally, the surface of these central stars is a mixture of helium, carbon, and oxygen resulting from partial helium burning. …