Sökning: "stellar evolution"

Visar resultat 1 - 5 av 77 avhandlingar innehållade orden stellar evolution.

  1. 1. On the Abundances of Li, Be and O in Metal-Poor Stars in the Galaxy

    Författare :Ana Elia García Pérez; Martin Asplund; Bengt Gustafsson; Francesca Primas; Beatriz Barbuy; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Astronomy; galactic evolution; stellar abundances; stellar atmospheres; spectral line formation; stellar mixing; Astronomi; Astronomy and astrophysics; Astronomi och astrofysik;

    Sammanfattning : Stellar atmospheres constitute excellent environments to study the chemical evolution of our Galaxy. The chemical composition of these atmospheres reflects the composition of the gas from where these stars were born. LÄS MER

  3. 2. Dwarf and Subgiant Stars as Probes of Galactic Chemical and Dynamical Evolution

    Författare :Patrik Thorén; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Astronomy; Abundances; atomic data; Galactic evolution; late-type stars; main sequence stars; subgiants; Pop II; Pop I; stellar evolution; Astronomi; Astronomy and astrophysics; Astronomi och astrofysik; astronomi; Astronomy;

    Sammanfattning : Stellar chemical abundances provide astronomers with vital information about the production of chemical elements. Some stars preserve the composition of the environment in which they were born on their surfaces. LÄS MER

  4. 3. On the Winds of Carbon Stars and the Origin of Carbon : A Theoretical Study

    Författare :Lars Mattsson; Susanne Höfner; Nils Bergvall; Kjell Olofsson; Martin Groenewegen; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; AGB stars; carbon stars; mass loss; stellar winds; circumstellar matter; cosmic dust; stellar evolution; nucleosynthesis; galactic chemical evolution; Astronomy and astrophysics; Astronomi och astrofysik; Astronomy; Astronomi; Fysik; Physics;

    Sammanfattning : Carbon is the basis for life, as we know it, but its origin is still largely unclear. Carbon-rich Asymptotic Giant Branch (AGB) stars (carbon stars) play an important rôle in the cosmic matter cycle and may contribute most of the carbon in the Galaxy. LÄS MER

  5. 4. Determination of stellar ages and star formation histories - a Bayesian approach With an application to nearby F and G stars

    Författare :Bjarne Rosenkilde Jørgensen; Astronomi - Genomgår omorganisation; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Astronomi; Astronomy; Galaxy evolution; Statistical methods; Stellar evolution; Data analysis;

    Sammanfattning : In order to understand the formation and evolution of the Galaxy it is imperative to know when different components formed. This means at the most basic level that we need to know the ages of stars. The present work demonstrates the many problems inherent in determining the ages of stars through comparison with stellar evolutionary models. LÄS MER

  7. 5. 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