EDP Sciences
Free access
Volume 438, Number 3, August II 2005
Page(s) 987 - 998
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20041858

A&A 438, 987-998 (2005)
DOI: 10.1051/0004-6361:20041858

V453 Oph: a s-process enriched, but carbon-deficient RV Tauri star of low intrinsic metallicity

P. Deroo1, M. Reyniers1, H. Van Winckel1, S. Goriely2 and L. Siess2

1  Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium
    e-mail: Pieter.Deroo@ster.kuleuven.be
2  Institut d'Astronomie et d'Astrophysique, Université Libre de Bruxelles, CP 226, 1050 Brussels, Belgium

(Received 18 August 2004 / Accepted 1 April 2005)

This paper reports the detection of a heavy element enriched RV Tauri variable with an abundance pattern that differs significantly from a standard s-process enriched object: . Based on optical high-resolution spectra, we determined that this object of low intrinsic metallicity ( $\rm [Fe/H]=-2.2$) has a mild, but significant, enrichment ( $\rm [s/Fe]\sim + 0.5$) of heavy elements for which the distribution points to slow neutron capture nucleosynthesis. This result is strengthened by a comparative analysis to the non-enriched RV Tauri star DS Aqr ( $\rm [s/Fe]= 0.0$). Although V453 Oph is the first RV Tauri star showing a strong s-process signature, it is not accompanied by C enhancement, challenging our current nucleosynthetic models of post-AGB stars that predict a simultaneous enrichment in C and s-process elements. The low N abundance excludes CN cycling as being responsible for the low C abundance. We explore three different scenarios to explain the heavy element distribution in this evolved object: an enrichment of the parental cloud, an accretion scenario in which the chemical patterns were acquired by mass transfer in a binary system and an intrinsic enrichment by dredge-up.

Key words: stars: abundances -- stars: evolution -- stars: AGB and post-AGB -- nuclear reactions, nucleosynthesis, abundances -- stars: individual: V453 Oph -- stars: individual: DS Aqr

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