Search for dissertations about: "stellar atmospheres"

Showing result 1 - 5 of 21 swedish dissertations containing the words stellar atmospheres.

2. 1. Stellar Winds of Cool Giants : Investigating the Mass-Loss Mechanism of AGB Stars

   Author : Sofie Liljegren; Susanne Höfner; Kjell Eriksson; Bernd Freytag; Hans Olofsson; Uppsala universitet; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; late-type stars; AGB stars; stellar winds; stellar atmospheres; dust; stellar pulsation; hydrodynamics; radiative transfer;

   Abstract : Asymptotic giant branch (AGB) stars are luminous cool giants of low to intermediate mass that are strongly pulsating and non-spherical, with heavy mass loss through a stellar wind. The mass loss makes these stars important for galactic chemistry, as the wind enriches the interstellar medium with new elements and dust, and it determines the final fate of these stars. READ MORE

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

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

   Abstract : 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. READ MORE

5. 3. Dynamical atmospheres and winds of M-type AGB stars

   Author : Sara Bladh; Susanne Höfner; Kjell Eriksson; Patricia Whitelock; Uppsala universitet; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; Late-type stars; AGB stars; stellar winds; atmospheres; mass-loss; outflows; circumstellar matter; dust; hydroynamics; radiative transfer; Astronomy with specialization in Astrophysics; Astronomi med intiktning mot astrofysik;

   Abstract : Mass loss, in the form of slow stellar winds, is a decisive factor for the evolution of cool luminous giants, eventually turning them into white dwarfs. These dense outflows are also a key factor in the enrichment of the interstellar medium with newly produced elements from the interior of these stars. READ MORE

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

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

   Abstract : 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. READ MORE

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

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

   Abstract : 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. READ MORE