Enrichment of Lead (Pb) in the Galactic Halo

We determined lead (Pb) abundances for 12 red giants with the stellar metallicity [Fe$/$H] ranging between $-2.1$ and $-1.3$ and its upper limits for 2 lower-metallicity objects, as well as lanthanum (La) and europium (Eu) abundances. The averages of [Pb$/$Fe] and [Pb$/$Eu] were $-0.3$ and $-0.6$, respectively, and no clear increase of these ratios with increasing metallicity was found. The [La$/$Eu] values are only slightly higher than that of the r-process component in solar-system material. These results, together with the previous studies for globular clusters, suggest a small contribution of the s-process to the Pb abundance of the field stars studied here, supporting an estimate of Pb production by the r-process from the solar-system abundances.