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Abstract: We discuss three effects of axial rotation at low metallicity. The first oneis the mixing of the chemical species which is predicted to be more efficientin low metallicity environments. A consequence is the production of importantquantities of primary $^{14}$N, $^{13}$C, $^{22}$Ne and a strong impact on thenucleosynthesis of the {\it s}-process elements. The second effect is aconsequence of the first. Strong mixing makes possible the apparition at thesurface of important quantities of CNO elements. This increases the opacity ofthe outer layers and may trigger important mass loss by line driven winds. Thethird effect is the fact that, during the main-sequence phase, stars, at verylow metallicity, reach more easily than their more metal rich counterparts, thecritical velocity\footnote{The critical velocity is the surface equatorialvelocity such that the centrifugal acceleration compensates for the localgravity.}. We discuss the respective importance of these three effects as afunction of the metallicity. We show the consequences for the early chemicalevolution of the galactic halo and for explaining the CEMP stars. We concludethat rotation is probably a key feature which contributes in an important wayto shape the evolution of the first stellar generations in the Universe.



Autor: Georges Meynet, Raphael Hirschi, Sylvia Ekstrom, Andre Maeder, Cyril Georgy, Patrick Eggenberger, Cristina Chiappini

Fuente: https://arxiv.org/







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