Helium variation due to self–pollution among Globular Cluster stars - Consequences on the horizontal branch morphology

  title={Helium variation due to self–pollution among Globular Cluster stars - Consequences on the horizontal branch morphology},
  author={Francesca D’Antona and Vittoria Caloi and Josefina Montalb{\'a}n and Paolo Ventura and R. Gratton INAF-OAR and Monteporzio and Italy IASF-CNR and Roma and Italy Inaf and Oap and Padova and Italy.},
  journal={Astronomy and Astrophysics},
It is becoming clear that "self-pollution" by the ejecta of massive asymptotic giant branch stars has an important role in the early chemical evolution of globular cluster stars, producing CNO abundance spreads which are observed also at the surface of unevolved stars. Observing that the ejecta which are CNO processed must also be helium enriched, we have modelled stellar evolution of globular cluster stars by taking into account this possible helium enhancement with respect to the primordial… 

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