Sökning: "Stars: abundances"

Visar resultat 6 - 10 av 42 avhandlingar innehållade orden Stars: abundances.

  1. 6. Asymptotic Giant Branch stars viewed up-close and far-off : The physics, chemistry, and evolution of their circumstellar envelopes

    Författare :Matthias Maercker; Hans Olofsson; Fredrik L. Schöier; Laurentius B. F. M. Waters; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; AGB stars; evolution; mass-loss; abundances; Astronomy; Astronomi; Astronomy; astronomi;

    Sammanfattning : The asymptotic giant branch (AGB) is the last stage of stellar evolution for stars with masses between 0.8-8 M(sun). This phase is characterised by an intense mass loss, which builds up a circumstellar envelope of dust and gas(CSE). It is through this process that the AGB stars contribute to the chemical evolution of galaxies. LÄS MER

  3. 7. Charting Circumstellar Chemistry of Carbon-rich AGB Stars

    Författare :Ramlal Unnikrishnan Nair; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; submillimeter: stars; astrochemistry; stars: mass-loss; circumstellar matter; stars: winds; outflows; Stars: AGB and post-AGB;

    Sammanfattning : Stars of low to intermediate initial masses (0.8 - 8 M⊙) enter the asymptotic giant branch (AGB) phase during their late evolution. LÄS MER

  4. 8. Studies of the S-type AGB star W Aquilae : The circumstellar envelope and the fain companion

    Författare :Taissa Danilovich; Chalmers tekniska högskola; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; stars: binaries: spectroscopic; circumstellar matter; stars: binaries: visual; stars: evolution; stars: mass-loss; stars: AGB and post-AGB; stars: individual: W Aql;

    Sammanfattning : Low- and intermediate-mass stars will all eventually enter the asymptotic giant branch (AGB) phase. AGB stars experience intense mass-loss, generating a significant fraction of the dust and molecular matter that enrichesthe ISM. AGB stars are also responsible for a the production of about half of all elements heavier than iron. LÄS MER

  5. 9. The nature of stars with a common origin: clues from metallicity, elemental abundances, and kinematics

    Författare :Cheng Liu; Astronomi - Genomgår omorganisation; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Stars: abundances; Galaxy: evolution; Galaxy: solar neighbourhood; Galaxy: bulge; Galaxy: globular clusters;

    Sammanfattning : Most of field stars originate from dissolved star clusters. If the gas cloud is well mixed the stars in the cluster are expected to be chemically homogenous. LÄS MER

  7. 10. Stochastic Chemical Evolution : A Study of Scatter in Relative Elemental Abundances in Extremely Metal-poor Stars

    Författare :Torgny Karlsson; Bengt Gustafsson; Mike Edmunds; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Astronomy; nucleosynthesis; chemical evolution; Galactic evolution; supernovae; chemical abundances; Population II stars; Astronomi; Astronomy and astrophysics; Astronomi och astrofysik;

    Sammanfattning : Chemical evolution addresses the problem of the formation of the chemical elements and their evolution throughout the history of the universe. This thesis discusses in particular the chemical evolution in the young universe and what we may learn from the observations of the oldest stars. LÄS MER