Issue |
A&A
Volume 461, Number 2, January II 2007
|
|
---|---|---|
Page(s) | 641 - 650 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20065893 | |
Published online | 09 October 2006 |
AGB nucleosynthesis in the Large Magellanic Cloud
Detailed abundance analysis of the RV Tauri star MACHO 47.2496.8
1
Instituut voor Sterrenkunde, Departement Natuurkunde en Sterrenkunde, K.U. Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium e-mail: maarten@ster.kuleuven.be
2
Dpto. Física Teórica y del Cosmos, Universidad de Granada, 18 071 Granada, Spain
3
SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, Scotland, UK
4
Department of Astronomy and Space Physics, Uppsala University, Box 515, 75120 Uppsala, Sweden
5
Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
Received:
23
June
2006
Accepted:
2
October
2006
Context.Abundance analysis of post-AGB objects as probes of AGB nucleosynthesis.
Aims.A detailed photospheric abundance study is performed on the carbon-rich post-AGB candidate MACHO 47.2496.8 in the LMC.
Methods.High-resolution, high signal-to-noise ESO VLT-UVES spectra of MACHO 47.2496.8 are analysed by performing detailed spectrum synthesis modelling using state-of-the-art carbon-rich MARCS atmosphere models.
Results.The spectrum of MACHO 47.2496.8 is not only dominated by bands of carbon bearing molecules, but also by lines of atomic transitions of s-process elements. The metallicity of [Fe/H] = -1.4 is surprisingly low for a field LMC star. The C/O ratio, however difficult to quantify, is greater than 2, and the s-process enrichment is large: the light s-process elements are enhanced by 1.2 dex compared to iron ([ls/Fe] = +1.2), while for the heavy s-process elements an even stronger enrichment is measured: [hs/Fe] = +2.1. The lead abundance is comparable to the [hs/Fe]. With its low intrinsic metallicity and its luminosity at the low end of the carbon star luminosity function, the star represents likely the final stage of a low initial mass star.
Conclusions.The LMC RV Tauri star MACHO 47.2496.8 is highly carbon and s-process enriched, and is most probable a genuine post-C(N-type) AGB star. This is the first detailed abundance analysis of an extragalactic post-AGB star to date.
Key words: stars: AGB and post-AGB / stars: abundances / stars: carbon / stars: individual: MACHO 47.2496.8 / Magellanic Clouds
© ESO, 2006
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