Sökning: "stars: abundances"

Visar resultat 21 - 25 av 42 avhandlingar innehållade orden stars: abundances.

1. 21. The death throes of massive stars

   Författare :Sofia Wallström; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; submillimeter: ISM -- ISM: supernova remnants -- ISM: individual objects: Cassiopeia A -- circumstellar matter -- stars: AGB and post-AGB -- stars: mass-loss -- stars: individual: IRAS 17163-3907 -- quasars: absorption lines -- quasars: individual: B 0218 357 -- galaxies: ISM -- galaxies: abundances -- ISM: molecules;

   Sammanfattning : Massive evolved stars affect their local surroundings as they go through phases of intense mass-loss and eventually explode as supernovae, adding kinetic energy and freshly synthesised material to the interstellar medium. The circumstellar material ejected by the star affects the shape and evolution of the future supernova remnant, and how the material is incorporated into the interstellar medium. LÄS MER

3. 22. Laboratory and Stellar Spectra in High Resolution: Studies of Fe, Pt and Tl in Peculiar Stars

   Författare :Gabriele Kalus; Fysiska institutionen; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; high-resolution spectroscopy; hyperfine structure; peculiar stars; iron; platinum; lead; upsilon Sagittarii; HR7775; chi Lupi; isotope shift; Atomic and molecular physics; Atom- och molekylärfysik; Fysicumarkivet A:1997:Kalus;

   Sammanfattning : The near-infrared spectrum of upsilon Sagittarii has been registered using the SOFIN high resolution spectrometer on the Nordic Optic Telescope, La Palma. For the first time 4f-5g transitions of Fe II in any astrophysical spectrum have been identified. LÄS MER

4. 23. Probing the effect of UV radiation on the chemistry in circumstellar envelopes around evolved stars

   Författare :Maryam Saberi; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Stars: abundances - Stars: AGB – Stars: individual: R Scl – Stars: binaries – Stars: carbon – Stars: circumstellar matter – Stars: chromospheres – Ultraviolet: stars;

   Sammanfattning : Low to intermediate mass (0.8 - 8 M⊙) stars lose a substantial amount of their mass in the last phase of stellar evolution, the asymptotic giant branch (AGB) phase. Hence, they are one of the main suppliers of dust and gas in the interstellar medium and important for the enrichment of galaxies. LÄS MER

5. 24. Exploring the Chemical Evolution of Globular Clusters and their Stars : Observational Constraints on Atomic Diffusion and Cluster Pollution in NGC 6752 and M4

   Författare :Pieter Gruyters; Andreas Korn; Piercarlo Bonifacio; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; stars: abundances – stars: atmospheres – stars: fundamental parameters – globular clusters: individual: NGC 6752 and M4 – techniques: spectroscopic; Astronomy with specialization in Astrophysics; Astronomi med intiktning mot astrofysik;

   Sammanfattning : Through the cosmic matter cycle, the chemical evolution of the Milky Way is imprinted in the elemental abundance patterns of late-type stars (spectral types F to K). Due to their long lifetimes ( 1 Hubble time), these stars are of particular importance when it comes to studying the build-up of elements during the early times of our Galaxy. LÄS MER

7. 25. UV Chemistry in the Circumstellar Envelopes of Evolved Stars

   Författare :Maryam Saberi; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Astrochemistry – molecular processes – stars: abundances – AGB – binaries – circumstellar matter – chromospheres – ultraviolet;

   Sammanfattning : Low- and intermediate-mass stars eject a substantial amount of their material into space during a late phase of stellar evolution, the asymptotic giant branch (AGB) phase. Therefore, they impact the chemistry of the interstellar medium. Due to the intense mass loss, a circumstellar envelope (CSE), rich in gas and dust, forms around the AGB star. LÄS MER