Sökning: "metallicity"

Visar resultat 21 - 25 av 25 avhandlingar innehållade ordet metallicity.

  1. 21. On the Chemical Composition of Metal-Poor Stars : Impact of Stellar Granulation and Departures from Local Thermodynamic Equilibrium on the Formation of Spectral Lines

    Författare :Remo Collet; Bengt Gustafsson; Martin Asplund; Roger Cayrel; Uppsala universitet; []
    Nyckelord :Astronomy; late-type stars; stellar abundances; stellar atmospheres; spectral line formation; convection; hydrodynamics; Galactic chemical evolution; Astronomi;

    Sammanfattning : The information about the chemical compositions of stars is encoded in their spectra. Accurate determinations of these compositions are crucial for our understanding of stellar nucleosynthesis and Galactic chemical evolution. LÄS MER

  3. 22. Atomic Processes in Stellar Atmospheres : Inelastic Collisions and Effects on Late-type Spectra

    Författare :Yeisson Fabian Martinez Osorio; Paul Barklem; Karin Lind; Nikolai Piskunov; Carlos Allende Prieto; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Spectral line: formation; atomic data; stellar abundances.; Fysik med inriktning mot astrofysik; Physics with specialization in Astrophysics;

    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

  4. 23. Young Stellar Clumps and Clusters in the Local Universe

    Författare :Matteo Messa; Göran Östlin; Angela Adamo; Petri Väisänen; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Astronomy; astronomi;

    Sammanfattning : The thesis introduces the process of star formation at the scale of galaxies, where a turbulent--dominated interstellar medium (ISM) can locally collapse under self-gravity. This collapse results in a star formation process which is hierarchical both in space and time. LÄS MER

  5. 24. An X-ray Spectroscopic Study of Perovskites Oxides and Halides for Emerging Devices

    Författare :Dibya Phuyal; Olof Karis; Manuel Bibes; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; perovskite oxides; halide perovskites; x-ray spectroscopy; electronic structure; Physics with spec. in Atomic; Molecular and Condensed Matter Physics; Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik;

    Sammanfattning : This thesis investigates the electronic structures on several perovskite oxide and halide materials with a focus on light harvesting applications. The systematic study of the electronic properties of the transition metal oxides and post-transition metal halides is a key point if one is to understand their properties. LÄS MER

  7. 25. Unveiling a multi-scale view of massive star and cluster formation

    Författare :Chi Yan Law; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; massive stars; methods:observation; magnetic field; stars:formation; ISM:clouds;

    Sammanfattning : Massive stars regulate the physical and chemical evolution of galaxies. Most stars within these galaxies, including massive ones, appear to be born in star clusters. However, there are many open questions about how these systems form from diffuse interstellar gas. LÄS MER