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Centro de Astrofísica da Universidade do Porto

Asteroseismic tests of element diffusion in solar type stars

S. Théado, S. Vauclair, M. Castro, S. Charpinet, N. Dolez

Abstract
Following the success of helioseismology, asteroseismology is now becoming a fundamental tool for penetrating the secrets of the internal structure of stars. In preparation of this new era in stellar physics, we study the effects of element diffusion on the computed frequencies of stellar oscillation modes for main-sequence solar-type stars. As the observed stars will be constrained by their atmospheric parameters, stellar models were computed with different physical inputs (whether including element diffusion or not) and iterated in order to fit the same observables (effective temperature, luminosity, surface chemical composition). The theoretical oscillation frequencies of these models were derived and compared. The results show that diffusion alters the internal structure of the models and their oscillation frequencies in a significant way. Although observational uncertainties in stellar external parameters are still important, comparisons between oscillation frequencies observed with the future space mission COROT and theoretically computed ones might provide evidence for diffusion processes in solar type stars.

Astronomy and Astrophysics
Volume 437, Page 553
July 2005

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Institute of Astrophysics and Space Sciences (IA) is a new but long anticipated research infrastructure with a national dimension. It embodies a bold but feasible vision for the development of Astronomy, Astrophysics and Space Sciences in Portugal, taking full advantage and fully realizing the potential created by the national membership of the European Space Agency (ESA) and the European Southern Observatory (ESO). IA resulted from the merging the two most prominent research units in the field in Portugal: the Centre for Astrophysics of the University of Porto (CAUP) and the Center for Astronomy and Astrophysics of the University of Lisbon (CAAUL). It currently hosts more than two-thirds of all active researchers working in Space Sciences in Portugal, and is responsible for an even greater fraction of the national productivity in international ISI journals in the area of Space Sciences. This is the scientific area with the highest relative impact factor (1.65 times above the international average) and the field with the highest average number of citations per article for Portugal.

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