Mixing of CNO-cycled matter in massive stars

  title={Mixing of CNO-cycled matter in massive stars},
  author={Norbert Przybilla and Markus Firnstein and M. Fernanda Nieva and Georges Meynet and A. Maeder Remeis Observatory BambergECAP and Mpa Garching and Geneva Observatory},
Aims. We test predictions of evolution models on mixing of CNO-cycled products in massive stars from a fundamental perspective. Relative changes within the theoretical C:N:O abundance ratios and the buildup of helium are compared with observational results. Methods. A sample of well-studied Galactic massive stars is presented. High-quality optical spectra are carefully analysed using improved NLTE line-formation and comprehensive analysis strategies. The results are put in the context of the… 

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