Heavy element abundances in low gravity globular cluster stars: NGC 362 and NGC 6388

Giant branch stars in the globular clusters NGC 362 and NGC 6388 were analysed for key s- and r-process element abundances. The NGC 362 stars showed comparable enhancements in the light and heavy s-process elements for the sample of 13 giant stars with values of 〈[ls/Fe] 〉 = 0.32 ± 0.10 dex and 〈[hs/Fe] 〉 = 0.46 ± 0.09 dex. The small spread in these values, as well as in the derived metallicity values (〈[Fe/H] 〉 = −1.21±0.09 dex), confirms the homogeneity of these elements in NGC 362. The two stars analysed in NGC 6388 showed enhancements in the light and heavy s-process elements with values of 〈[ls/Fe] 〉 = 0.58±0.13 dex and 〈[hs/Fe] 〉 = 0.39 ± 0.07 dex. The light s-process elements are more enhanced in this metal-rich cluster compared to the heavy s-process elements. The derived metallicity was in good agreement between the two stars with the mean value for the cluster of 〈[Fe/H] 〉 = −0.60 ± 0.02 dex. Due to the similar metallicity of NGC 6388 with 47 Tuc, these two stars were compared with the results from Worley et al. where giant branch stars in 47 Tuc were analysed. The heavy element enhancements between the two clusters were found to be very similar indicating that the relative enhancements of ls and hs elemental abundances is metallicity dependent