Red Giant Universe 2.1 Mac Download [WORK]
We present abundance measurements for a large number of neutron-capture elements in giant stars of the globular clusters M4, M5, and M13. The relative abundance ratios differ between all three clusters. For all clusters, we find that the mean abundances for the elements from Ba to Hf can be well explained by scaled versions of the solar s- and r-process abundances, albeit with different mixtures of s- and r-process material for each clusters.
Red Giant Universe 2.1 Mac Download
Elements heavier than iron are produced in asymptotic giant branch (AGB) stars via the slow neutron capture process (s process). Recent observations of s-process-enriched Carbon Enhanced Metal-Poor (CEMP) stars have provided an unprecedented wealth of observational constraints on the operation of the s-process in low-metallicity AGB stars. We present new preliminary full network calculations of low-metallicity AGB stars, including a comparison to the composition of a few s-process rich CEMP stars. We also discuss the possibility of using halo planetary nebulae as further probes of low-metallicity AGB nucleosynthesis.
We explore the general characteristics of extremely metal-poor (EMP) stars in the Galaxy using the Stellar Abundances for Galactic Archaeology (SAGA) database (Suda et al. 2008, PASJ, 60, 1159). The overall trend of EMP stars suggests that there are at least two types of extra mixing to change the surface abundances of EMP stars. One is to deplete lithium abundance during the early phase of giant branch and another is to decrease C/N ratio by one order of magnitude during the red giant branch or AGB phase. On the other hand, these mixing processes are different from those suggested in the Galactic globular clusters because of the different relations between O, Na, Mg, and Al abundances.