The study of s-process nucleosynthesis based on barium stars, CEMP-s and CEMP-r/s stars

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

“…In our metal-rich barium stars, almost all of the r values are lower than 0.1, except for HD 130386 and HD 100012. This supports the conclusion that single neutron exposure events (usually with r ≤ 0.1) for the s-process nucleosynthesis probable exist throughout the entire metallicity range of the Galaxy evolution (Cui et al 2013a). Furthermore, the occurrence frequency of single exposure events is very high in metal-rich conditions.…”

“…5, bottom panel). When a mixed contribution of the r-and s-process nucleosynthesis was considered, the observed abundance patterns of CEMP-r/s stars were able to be fitted well by the theoretical predictions (Cui et al 2007(Cui et al , 2010(Cui et al , 2013aBisterzo et al 2009). This is also correct for almost all metal-poor and metal-rich barium stars including all r-rich metal-rich barium stars.…”

“…We used C r ≥ 5.0 as the reference value to judge whether a star belonged to the r-rich barium star group. In fact, this value is lower than 2.0 in most normal barium stars (Cui et al 2013a). …”

“…seems that these six metal-rich barium stars belong to an independent group because they have similar abundance characteristics with the r-rich stars. For the metal-poor barium stars, however, this is not the case (Cui et al 2013a, see their Tables 1, 2). …”

“…Figure 4 also shows that the CEMP-r/s stars are spread in a wide range of [La/Nd] about from −0.4 to 0.3. Much effort has been made to solve the problem of the origin of CEMP-r/s stars (Cui et al 2010(Cui et al , 2013aBisterzo et al 2009). Commonly, a mixed origin is assumed that the observed CEMP-r/s star had been successively polluted by the s-and r-process materials, although the accurate site for the r-process nucleosynthesis is still uncertain.…”