58 research outputs found
Element Settling in the Solar Interior
Element settling inside the Sun now becomes detectable from the comparison of
the observed oscillation modes with the results of the theoretical models. This
settling is due, not only to gravitation, but also to thermal diffusion and
radiative acceleration (although this last effect is small compared to the two
others). It leads to abundance variations of helium and heavy elements of
below the convective zone. Although not observable from
spectroscopy, such variations lead to non-negligible modifications of the solar
internal structure and evolution. Helioseismology is a powerful tool to detect
such effects, and its positive results represent a great success for the theory
of stellar evolution. Meanwhile, evidences are obtained that the element
settling is slightly smoothed down, probably due to mild macroscopic motions
below the convective zone. Additional observations of the abundances of both
Solar Li and He lead to specific constraints on these particular
motions.Comment: 9 pages, 2 figures, paper presented at the workshop on Solar
Composition and its Evolution - From Core to Corona, Berne, 26-30 January 9
Seismic tests of accretion in central stars of planetary systems
Central stars of extra-solar planetary systems are metal-rich. Planet
accretion or initial surmetallicity can explain this observationnal fact. These
scenarios can be tested with asteroseismology. We calibrate two stellar models,
one with accretion and one with high initial metallicity, in order to obtain
the same external parameters for both of them. We then compare their internal
structures and their oscillation frequencies.Comment: 4 pages, 2 figures, ASP Conferences Series, D.W. Kurtz & Karen
Pollarrd, Ed
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