Abundance Patterns in S-type AGB stars : Setting Constraints on Nucleosynthesis and Stellar Evolution Models

During the evolution on the AGB, S-type stars are the first objects to experience s-process nucleosynthesis and third dredge-ups, and therefore to exhibit sprocess signatures in their atmospheres. Their significant mass loss rates (10^-7 to 10^-6 M*/year) make them major contributors to the AGB nucleosynthesis yields at solar metallicity. Precise abundance determinations in S stars are of the utmost importance for constraining e.g. the third dredge-up luminosity and efficiency (which has been only crudely parameterized in all current nucleosynthetic models so far). Here, dedicated S-star model atmospheres are used to determine precise abundances of key s-process elements, and to set constraints on nucleosynthesis and stellar evolution models. A special interest is paid to technetium, an element with no stable isotopes (99Tc, the only isotope produced by the s-process in AGB stars, has a half-life of 2.1 x 10^5 years). Its detection is considered as the best signature that the star effectively populates the thermally-pulsing AGB phase of evolution. The derived Tc/Zr abundances are compared, as a function of the derived [Zr/Fe] overabundances, with AGB stellar model predictions. The [Zr/Fe] overabundances are in good agreement with the model predictions, while the Tc/Zr abundances are slightly overpredicted. This discrepancy can help to set better constraints on nucleosynthesis and stellar evolution models of AGB stars.Comment: 5 pages, 3 figures, To be published in the proceedings of the conference "Why Galaxies Care about AGB Stars II", held in Vienna, August 16-20, 2010; eds Franz Kerschbaum, Thomas Lebzelter, and Bob Wing, ASP Conf. Serie

UNIFIED EQUATION OF STATE FOR SUPERNOVA CORES AND NEUTRON STARS USING THE ENERGY-DENSITY FUNCTIONAL THEORY

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Extended Skyrme Interaction in the Spin Channel

Most of the Skyrme interactions are known to predict spin or isospin instabilities beyond the saturation density of nuclear matter which contradict predictions based on realistic interactions. A modification of the standard Skyrme interaction is proposed so that the ferromagnetic instability is removed. The new terms are density dependent and modify only the spin p-h interaction in the case of spin-saturated system. We have shown that these new terms change the total binding energy of odd-nuclei by only few tenths of keV. From the analysis of the spin instabilities of nuclear matter, restrictions on the parameters governing the spin-density dependent terms are evaluated. We conclude that with the extended Skyrme interaction, the Landau parameters G 0 and G 0 could be tuned with a large flexibility without changing the ground-state properties in nuclei and in nuclear matter.SCOPUS: cp.jinfo:eu-repo/semantics/publishe

Cent scientifiques répliquent à SEA (Suppression des Expériences sur l’Animal vivant) et dénoncent sa désinformation

La lutte contre la maltraitance animale est sans conteste une cause moralement juste. Mais elle ne justifie en rien la désinformation à laquelle certaines associations qui s’en réclament ont recours pour remettre en question l’usage de l’expérimentation animale en recherche

Nucleosynthesis: a field with still many open nuclear physics questions

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Nuclear masses and the r- and p-processes of nucleosynthesis

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Spallation nucleosynthesis by accelerated charged-particles in stellar envelopes of magnetic stars

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Nucleosynthesis: a field with still many open nuclear physics questions

info:eu-repo/semantics/publishe