Search for dissertations about: "Astronomy and astrophysics"

Showing result 11 - 15 of 462 swedish dissertations containing the words Astronomy and astrophysics.

  2. 11. Magnetic and Chemical Structures in Stellar Atmospheres

    Author : Oleg Kochukhov; Nikolai Piskunov; Georges Michaud; Uppsala universitet; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; Astronomy; chemically peculiar stars; high-resolution spectroscopy; magnetic fields; Doppler imaging; rapidly oscillating Ap stars; Astronomi; Astronomy and astrophysics; Astronomi och astrofysik; Astronomy; Astronomi;

    Abstract : We present an investigation of the magnetic field geometries and inhomogeneous distribution of chemical elements in the atmospheres of peculiar A and B stars. Our study combines high-quality spectroscopic and spectropolarimetric stellar observations with the development and application of novel techniques for theoretical interpretation of the shapes and variability of stellar line profiles. READ MORE

  4. 12. Molecules and Dust around AGB stars : Mass-loss rates and molecular abundances

    Author : Sofia Ramstedt; Hans Olofsson; Fredrik Schöier; José Cernicharo; Stockholms universitet; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; AGB stars; mass-loss; circumstellar abundances; Formation and development of stars; Stjärnors bildning och utveckling; Astronomy; astronomi;

    Abstract : All stars with a stellar mass of about 0.8–8 MSun will end their lives as asymptotic giant branch (AGB) stars. Through their extensive mass loss the AGB stars constitutes an important source of nuclear processed material. READ MORE

  5. 13. A Study of Grain Drift in C Stars : Theoretical Modeling of Dust-Driven Winds in Carbon-Rich Pulsating Giant Stars

    Author : Christer Sandin; Susanne Höfner; Bengt Gustafsson; Lee Anne Willson; Uppsala universitet; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; Astronomy; hydrodynamics; radiative transfer; instabilities; dust formation; stars: AGB and post-AGB; stars: mass-loss; stars: variables: general; Astronomi; Astronomy and astrophysics; Astronomi och astrofysik; Theoretical Astrophysics; teoretisk astrofysik;

    Abstract : A major fraction of stars will pass through a short period of dramatic events in their final evolutionary stage. Low- to intermediate-mass stars, studied here, are stripped of their outer parts in a slow massive wind. This mass loss reshapes both the star and the surrounding medium. READ MORE

  6. 14. The faintest stars : A study of white, red and brown dwarfs

    Author : Leif Festin; Uppsala universitet; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; Astronomy; brown dwarfs; white dwarfs; M dwarf; low luminosity; luminosity function; mass function; Pleiades; Astronomi; Astronomy and astrophysics; Astronomi och astrofysik; astronomi; Astronomy;

    Abstract : The local space density of the faintest stars, including M dwarfs, white dwarfs and brown dwarfs has been studied by two different methods.By using dark nebulae as opaque outer screens, the luminosity functions of M dwarfs and white dwarfs were studied as volume-limited and dynamically unbiassed foreground samples. READ MORE

  7. 15. Chemical Abundance Analysis of Population II Stars : The Summary Includes a Background in General Astronomy

    Author : Karin Jonsell; Bengt Gustafsson; Bengt Edvardsson; Paul Barklem; Christopher Sneden; Uppsala universitet; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; Astronomy; Astronomy; Galactic evolution; Halo; Milky Way; Oxygen; r-element; s-element; Stellar abundances; Astronomi; Astronomy and astrophysics; Astronomi och astrofysik;

    Abstract : We are made of stardust in the sense that most atomic nuclei around us have been formed by stars. Stars synthesise new elements and expel them to the interstellar medium, from which later new generations of stars are born. We can map this chemical evolution by analysing the atmospheric contents of old Galactic halo stars. READ MORE