Heavy elements in barium stars

ABSTRACT New elemental abundances for the neutron-capture elements Sr, Nb, Mo, Ru, La, Sm, and Eu are presented a large sample of 180 barium (Ba) giant stars, class chemically peculiar objects that exhibit in their spectra enhancements created by s-process, as consequence mass transfer between components binary system. The content heavy these fact, points to nucleosynthesis mechanisms took place within former asymptotic branch (AGB) companion, now an invisible white dwarf. From high-resolution ($R=48\, 000$) optical, we derived either equivalent width measurements or synthetic computations, compared them with available data field dwarf stars same range metallicity. A re-determination La resulted [La/Fe] ratios up 1.2 dex lower than values previously reported literature. programme Ba show overabundance elements, except Eu, which observational set behave similarly stars. Comparison model predictions satisfactory second-to-first s-process peak (e.g. [La/Sr]) predominantly r-process element La. However, observed [Nb, Ru/Sr] [Ce, Nd, Sm/La] median higher at upper limits ranges predictions. This unexplained feature calls new neutron capture models be investigated.