Sökning: "Astrophysics - Solar and Stellar Astrophysics"
Visar resultat 1 - 5 av 34 avhandlingar innehållade orden Astrophysics - Solar and Stellar Astrophysics.
1. Theoretical Atomic Spectroscopy of Earthbound and Stellar Plasma
Sammanfattning : Motivated by spectroscopic analysis of astrophysical and laboratory plasma, this thesis concerns the fundamental structure and spectral properties of atoms and their ions. The multiconfiguration Dirac-Hartree-Fock (MCDHF) method is used to predict the emission or absorption of radiation, by atomic systems in general, and of heavy and highly charged ions in particular. LÄS MER
2. Atomic Processes in Stellar Atmospheres : Inelastic Collisions and Effects on Late-type Spectra
Sammanfattning : Chemical abundances as measured from stellar spectral lines are often subject to uncertainties due to lack of accurate data for inelastic collisions, which is needed for non-local thermodynamic equilibrium (non-LTE) modelling. For cool stars, understanding of collision processes with electrons and hydrogen atoms is required to achieve high precision measurements. LÄS MER
3. Stellar kinematics in surveys and simulations
Sammanfattning : We study stellar motions in the Milky Way with N-body simulations and large astrometric samples from ESA's Gaia mission. We identify two kinematic populations for white dwarfs in the Solar neighbourhood. We also investigate the accreted halo and reveal two new structures. LÄS MER
4. Experimental and Computational Atomic Spectroscopy for Astrophysics : Oscillator strengths and lifetimes for Mg I, Si I, Si II, Sc I, and Sc II
Sammanfattning : Atomic data such as oscillator strengths and wavelengths are important for astrophysical applications as they have a crucial role in determining abundances of specific elements in a star, a galaxy, or any object emitting radiation in the space. Stars in the Galaxy mostly keep the composition of the interstellar gas from which they were formed, therefore studying stellar abundances helps us understand how the Milky Way was formed and how it evolved. LÄS MER
5. Advances in Stellar Astrophysics from Laboratory Spectroscopy
Sammanfattning : Investigation of astrophysical plasmas, such as stellar atmospheres, require both knowledge of atomic structure and data. We present laboratory instruments, techniques and tools for acquisition of the data required to derive important atomic parameters such as, wavelengths, oscillator strengths and line profiles. LÄS MER
