Journal Article

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

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

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 396, issue 4, pages 2313-2318
Published in print July 2009 | ISSN: 0035-8711
Published online July 2009 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.14900.x
The depletion of carbon by extra mixing in metal-poor giants

Show Summary Details

Preview

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.

Keywords: stars: AGB and post-AGB; stars: carbon; stars: evolution; stars: Population II

Journal Article.  4707 words.  Illustrated.

Subjects: Astronomy and Astrophysics

Full text: subscription required

How to subscribe Recommend to my Librarian

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.