Sökning: "Astronomi och astrofysik"

Visar resultat 21 - 25 av 471 avhandlingar innehållade orden Astronomi och astrofysik.

1. 21. An Observational Study of Accretion Processes in T Tauri Stars

   Författare :Henricus Cornelis Stempels; Nikolai Piskunov; Gibor Basri; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Astronomy; Star formation; T Tauri stars; Emission lines; Accretion; NLTE radiative transfer; Astronomi; Astronomy and astrophysics; Astronomi och astrofysik; Astronomy; Astronomi;

   Sammanfattning : This thesis is a detailed observational study of the accretion processes in T Tauri stars (TTS). The interaction between the central star, the circumstellar disk and the magnetic field gives rise to a wide range of features in the spectra of TTS. LÄS MER

3. 22. Theoretical Atomic Spectroscopy of Earthbound and Stellar Plasma

   Författare :Jon Grumer; Matematisk fysik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; atomstruktur; atomära processer; elektronkorrelation; plasmaspektroskopi; magnetfält; hyperfinstruktur; solkoronan; rymdväder; förekomst av grundämnen i stjärnor; datorsimuleringar; Zeemaneffekt; relativistiska effekter; atomic structure; atomic processes; computer simulation; electron correlation; relativistic atomic theory; plasma spectroscopy; Zeeman effect; magnetic fields; hyperfine structure; solar corona; space weather; stellar abundances; Fysicumarkivet A:2016:Grumer;

   Sammanfattning : Motivated by spectroscopic analysis of astrophysical and laboratory plasma, this thesis concerns the fundamental structure and spectral properties of atoms and their ions. The multiconfiguration Dirac-Hartree-Fock (MCDHF) method is used to predict the emission or absorption of radiation, by atomic systems in general, and of heavy and highly charged ions in particular. LÄS MER

4. 23. Many-body Problems in the Theory of Stellar Collapse and Neutron Stars

   Författare :Emma Olsson; Bengt Gustafsson; Christopher Pethick; Bengt Friman; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Astronomy; neutron stars; core-collapse supernovae; response functions; Fermi liquids; nuclear matter; neutrino interactions; Astronomi; Astronomy and astrophysics; Astronomi och astrofysik;

   Sammanfattning : When modelling the collapse of massive stars leading to supernova explosions and the cooling of neutron stars, understanding the microphysical processes, such as the interaction of neutrinos within a dense medium are of vital importance. The interaction of neutrinos with nucleons (neutrons and protons) is altered by the presence of the medium, compared to the same process with free nucleons. LÄS MER

5. 24. Super Star Clusters in Blue Compact Galaxies : Evidence for a near-infrared flux excess and properties of the starburst phase

   Författare :Angela Adamo; Göran Östlin; Erik Zackrisson; Richard de Grjis; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; starburst galaxy-extragalactic star clusters-dwarf merger; Astronomy and astrophysics; Astronomi och astrofysik; Astronomy; astronomi;

   Sammanfattning : Luminous Blue compact galaxies (BCGs) are metal-poor actively star-forming systems, characterised by bright ultraviolet and blue luminosities. Hubble Space Telescope high-resolution data have revealed that the luminous star-forming knots in these galaxies are composed of hundreds of young massive star clusters. LÄS MER

7. 25. X-ray variability in Galactic high-mass black hole binaries

   Författare :Magnus Axelsson; Stefan Larsson; Chris Done; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Accretion; high-energy astrophysics; temporal variability; X-ray binaries; Astronomy and astrophysics; Astronomi och astrofysik; Astronomy; astronomi;

   Sammanfattning : The stars of the night sky can to the naked eye appear to be steady and unchanging, apart from the twinkling created by air moving in the atmosphere. However, when viewed in X-rays, the sky is far from constant, with detectable changes occurring on very short timescales.Black hole X-ray binaries are strong sources of X-rays. LÄS MER