A strongly s-process enriched RV Tauri star in the LMC.
Abstract
A detailed abundance analysis is presented of an intriguing object in the Large Magellanic Cloud that links the class of RV Tauri stars to the post-AGB phase of evolution: MACHO 47.2496.8. The spectrum, taken with VLT-UVES, is dominated by molecular lines of carbon bearing molecules, together with strong transitions of s-process species. Detailed spectral syntheses were made using a state-of-the-art carbon rich MARCS model. A surprisingly low metallicity ([Fe/H] = -1.4), together with strong carbon (C/O>2) and s-process overabundances were found, reaching values of [ls/Fe] = +1.2 for the light s-process elements, and even [hs/Fe] = +2.1 for the heavy ones. The strong s-process enhancements are in agreement with the theoretical expectations at that metallicity. Only the combination of a low lead content and a high [hs/ls] is not easily explained by the current nucleosynthetic models. It is not clear whether this star is intrisically or extrinsically enriched, but several arguments favour an intrisic enrichment, implying the object to be a genuine post carbon (N-type) AGB star. With the low metallicity and a luminosity at the very low end of the carbon star luminosity function, MACHO 47.2496.8 represents the final evolutionary state of a star of low initial mass.
Based on observations collected at ESO, Chile (programme 074.D-0619(A))- Publication:
-
Memorie della Societa Astronomica Italiana
- Pub Date:
- 2006
- Bibcode:
- 2006MmSAI..77..949R
- Keywords:
-
- Stars: AGB and post-AGB;
- Stars: abundances;
- Stars: carbon;
- Stars: individual: MACHO 47.2496.8;
- Magellanic Clouds