Possible discovery of the r-process characteristics in the abundances of metal-rich barium stars

Abstract

Aims. We study the abundance distributions of a sample of metal-rich barium stars provided by Pereira et al. (2011, A&A, 533, A51) to investigate the s-and r-process nucleosynthesis in the metal-rich environment. Methods. We compared the theoretical results predicted by a parametric model with the observed abundances of the metal-rich barium stars. Results. We found that six barium stars have a significant r-process characteristic, and we divided the barium stars into two groups: r-rich barium stars (Cr > 5.0, [La/Nd] < 0) and normal barium stars. The behavior of the r-rich barium stars seems more like that of the metal-poor r-rich and CEMP-r/s stars. We suggest that the most possible formation mechanism for these stars is the s-process pollution, although their abundance patterns can be fitted very well when the pre-enrichment hypothesis is included. That we cannot explain them well using the s-process nucleosynthesis alone may be due to our incomplete knowledge on the production of Nd, Eu, and other relevant elements by the s-process in metal-rich and super metal-rich environments (see details in Pereira et al. 2011). © ESO, 2014.