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Published online by Cambridge University Press: 09 March 2010
We have performed deep high-dispersion spectroscopy to examine enhancement of s-process elements in the exremely metal-poor ([Ar/H]~−2.1) halo planetary nebulae H4-1 and BoBn1 using the 8.2-m Subaru telescope/High-Dispersion Spectrograph (HDS). We have detected several emission lines of s-process elements in H4-1 and BoBn1, and we have found that the enhancement of heavy s-process elements in these objects is comparable with that in s-process enhanced CEMP stars with [Fe/H]>−2.5. The C- and N-rich abundances of H4-1 and BoBn1 might be explained by binary evolution models. We have detected 5 fluorine lines in BoBn1. The re-estimated F abundance using these lines is [F/H]=+1.4±0.1.