Sökning: "stellar mass-loss"

Visar resultat 11 - 15 av 20 avhandlingar innehållade orden stellar mass-loss.

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

   Författare :Christer Sandin; Susanne Höfner; Bengt Gustafsson; Lee Anne Willson; Uppsala universitet; []
   Nyckelord :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;

   Sammanfattning : 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. LÄS MER

3. 12. Modelling the Winds from Carbon Rich AGB Stars : Implications for Stellar Evolution and the Chemical Evolution of Galaxies

   Författare :Lars Mattsson; Uppsala universitet; []
   Nyckelord :;

   Sammanfattning : Stars on the AGB are known to lose mass at high rates (10-8 - 10-4 Msun/yr) through slow winds (20 km/s), enriching the inter stellar medium with newly synthesised elements. We explore how the mass loss for C-rich AGB stars depends on the basic stellar parameters by computing a large grid of wind models. LÄS MER

4. 13. 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

5. 14. 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

7. 15. 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