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Photograph of Ross Church

Ross Church

Senior lecturer

Photograph of Ross Church

The depletion of carbon by extra mixing in metal-poor giants

Author

  • Richard J. Stancliffe
  • Ross P. Church
  • George C. Angelou
  • John C. Lattanzio

Summary, in English

There is an apparent dichotomy between the metal-poor ([Fe/H] ≤ -2) yet carbon-normal giants and their carbon-rich counterparts. The former undergo significant depletion of carbon on the red giant branch after they have undergone first dredge-up, whereas the latter do not appear to experience significant depletion. We investigate this in the context that the extra mixing occurs via the thermohaline instability that arises due to the burning of 3He. We present the evolution of [C/Fe], [N/Fe] and 12C/13C for three models: a carbon-normal metal-poor star, and two stars that have accreted material from a 1.5 M AGB companion, one having received 0.01 M of material and the other having received 0.1 M. We find the behaviour of the carbon-normal metal-poor stars is well reproduced by this mechanism. In addition, our models also show that the efficiency of carbon-depletion is significantly reduced in carbon-rich stars. This extra-mixing mechanism is able to reproduce the observed properties of both carbon-normal and carbon-rich stars.

Publishing year

2009-07-01

Language

English

Pages

2313-2318

Publication/Series

Monthly Notices of the Royal Astronomical Society

Volume

396

Issue

4

Document type

Journal article

Publisher

Oxford University Press

Topic

  • Astronomy, Astrophysics and Cosmology

Keywords

  • Stars: AGB and post-AGB
  • Stars: carbon
  • Stars: evolution
  • Stars: Population II

Status

Published

ISBN/ISSN/Other

  • ISSN: 0035-8711