s- and r-process element abundances in the CMD of 47 Tucanae using the Robert Stobie Spectrograph on SALT

摘要

A recent study by Wylie et al 2006 has revealed that s-process elementabundances are enhanced relative to iron in both red giant branch andasymptotic giant branch stars of 47 Tucanae. A more detailed investigation intos-process element abundances throughout the colour-magnitude diagram of 47Tucanae is vital in order to determine whether the observed enhancements areintrinsic to the cluster. This paper explores this possibility throughobservational and theoretical means. The visibility of s- and r-process elementlines in synthetic spectra of giant and dwarf stars throughout the colourmagnitude diagram of 47 Tucanae has been explored. It was determined that aresolving power of 10 000 was sufficient to observe s-process element abundancevariations in globular cluster giant branch stars. These synthetic results werecompared with the spectra of eleven 47 Tucanae giant branch stars observedduring the performance verification of the Robert Stobie Spectrograph on theSouthern African Large Telescope. Three s-process elements, Zr, Ba, Nd, and oner-process element, Eu, were investigated. No abundance variations were foundsuch that [X/Fe] = 0.0 +/- 0.5 dex. It was concluded that this resolving power,R ~ 5000, was not sufficient to obtain exact abundances but upper limits on thes-process element abundances could be determined.