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The s-process in Rotating AGB Stars

Published online by Cambridge University Press:  26 May 2016

Falk Herwig
Affiliation:
University of Victoria, Victoria, BC, Canada; fherwig@uvastro.phys.uvic.ca
Norbert Langer
Affiliation:
Universiteit Utrecht, Utrecht, The Netherlands; N.Langer@astro.uu.nl
Maria Lugaro
Affiliation:
IoA, University of Cambridge, Cambridge, UK; mal@ast.cam.ac.uk

Abstract

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We discuss the occurrence of the s-process during the radiative interpulse phase of rotating AGB stars. Due to differential rotation, protons are mixed into 12C-rich layers after thermal pulses, in the course of the so called third dredge up episode. We follow the time evolution of key isotope abundances in the relevant layers with a post-processing code which includes time dependant mixing and nucleosynthesis. In rotating AGB models, the mixing persists during the entire interpulse phase due to the steep gradient of angular velocity at the envelope-core interface. As the layers containing protons and 12C, which are formed this way, become hotter, a 13C-pocket is formed in a natural way. However, in this situation also 14N is formed and spread over the entire 13C-pocket. We include the neutron consuming 14N(n,p) reaction in our network and determine to what extent it reduces the production of trans-iron elements. We propose that rotation may be responsible for the spread of efficiencies of the 13C neutron source as required by observations.

Type
Part III: Planetary Nebulae in the Scheme of Stellar Evolution
Copyright
Copyright © Astronomical Society of the Pacific 2003 

References

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