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

Stancliffe, Richard J. ; Church, Ross P. LU orcid ; Angelou, George C. and Lattanzio, John C. (2009) In Monthly Notices of the Royal Astronomical Society 396(4). p.2313-2318
Abstract

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... (More)

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.

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author
; ; and
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Stars: AGB and post-AGB, Stars: carbon, Stars: evolution, Stars: Population II
in
Monthly Notices of the Royal Astronomical Society
volume
396
issue
4
pages
6 pages
publisher
Oxford University Press
external identifiers
  • scopus:67649888014
ISSN
0035-8711
DOI
10.1111/j.1365-2966.2009.14900.x
language
English
LU publication?
no
id
76c6a538-e4ef-4c70-9297-67f2df70531c
date added to LUP
2019-06-05 14:15:27
date last changed
2022-01-31 21:31:02
@article{76c6a538-e4ef-4c70-9297-67f2df70531c,
  abstract     = {{<p>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 <sup>3</sup>He. We present the evolution of [C/Fe], [N/Fe] and <sup>12</sup>C/<sup>13</sup>C for three models: a carbon-normal metal-poor star, and two stars that have accreted material from a 1.5 M<sub>⊙</sub> AGB companion, one having received 0.01 M<sub>⊙</sub> of material and the other having received 0.1 M<sub>⊙</sub>. 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.</p>}},
  author       = {{Stancliffe, Richard J. and Church, Ross P. and Angelou, George C. and Lattanzio, John C.}},
  issn         = {{0035-8711}},
  keywords     = {{Stars: AGB and post-AGB; Stars: carbon; Stars: evolution; Stars: Population II}},
  language     = {{eng}},
  month        = {{07}},
  number       = {{4}},
  pages        = {{2313--2318}},
  publisher    = {{Oxford University Press}},
  series       = {{Monthly Notices of the Royal Astronomical Society}},
  title        = {{The depletion of carbon by extra mixing in metal-poor giants}},
  url          = {{http://dx.doi.org/10.1111/j.1365-2966.2009.14900.x}},
  doi          = {{10.1111/j.1365-2966.2009.14900.x}},
  volume       = {{396}},
  year         = {{2009}},
}