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Photograph of Ross Church

Ross Church

Senior lecturer

Photograph of Ross Church

Thermohaline Mixing And Its Role In The Evolution Of Carbon And Nitrogen Abundances In Globular Cluster Red Giants: The Test Case Of Messier 3

Author

  • George C. Angelou
  • Ross Church
  • Richard J. Stancliffe
  • John C. Lattanzio
  • Graeme H. Smith

Summary, in English

We review the observational evidence for extra mixing in stars on the red giant branch (RGB) and discuss why thermohaline mixing is a strong candidate mechanism. We recall the simple phenomenological description of thermohaline mixing and aspects of mixing in stars in general. We use observations of M3 to constrain the form of the thermohaline diffusion coefficient and any associated free parameters. This is done by matching [C/Fe] and [N/Fe] along the RGB of M3. After taking into account a presumed initial primordial bimodality of [C/Fe] in the CN-weak and CN-strong stars, our thermohaline mixing models can explain the full spread of [C/Fe]. Thermohaline mixing can produce a significant change in [N/Fe] as a function of absolute magnitude on the RGB for initially CN-weak stars, but not for initially CN-strong stars, which have so much nitrogen to begin with that any extra mixing does not significantly affect the surface nitrogen composition.

Department/s

  • Lund Observatory

Publishing year

2011

Language

English

Publication/Series

Astrophysical Journal

Volume

728

Issue

2

Document type

Journal article

Publisher

American Astronomical Society

Topic

  • Astronomy, Astrophysics and Cosmology

Keywords

  • globular clusters: individual (M3)
  • stars: abundances
  • stars:
  • evolution
  • stars: Population II

Status

Published

ISBN/ISSN/Other

  • ISSN: 0004-637X