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Abstract: We report on an investigation into stellar evolution and nucleosynthesis inthe low and extremely low metallicity regime, including models of stars with apure Big Bang composition i.e. Z=0. The metallicity range of the extremelymetal poor EMP models we have calculated is -6.5 < Fe-H < -3.0, whilst ourmodels are in the mass range 0.85 < M < 3.0 Msun. Many of the EMP and Z=0models experience violent evolutionary episodes not seen at highermetallicities. We refer to these events as `Dual Flashes- since they arecharacterised by peaks in the hydrogen and helium burning luminositiesoccurring at roughly the same time. Some of the material processed by theseevents is later dredged up by the convective envelope, causing signifcantsurface pollution. These events have been reported by previous studies, so ourresults reaffirm their occurrence - at least in 1D stellar models. The noveltyof this study is that we have calculated the entire evolution of the Z=0 andEMP models, from the ZAMS to the end of the TPAGB, including detailednucleosynthesis. We have also calculated the nucleosynthetic yields, which willsoon be available in electronic format. Although subject to many uncertaintiesthese are, as far as we are aware, the only yields available in this mass andmetallicity range. In this paper we briefy describe some of the results in thecontext of abundance observations of EMP halo stars. This work formed part ofSWC-s PhD thesis completed in March 2007 and a series of subsequent paperswill describe the results of the study in more detail.



Autor: Simon W. Campbell, John C. Lattanzio

Fuente: https://arxiv.org/







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