Enrichment of lead (Pb) in the Galactic halo

TL;DR

This study measures lead abundances in red giants across different metallicities to understand its nucleosynthesis origins, finding little evidence of s-process contribution and supporting r-process dominance in Galactic halo stars.

Contribution

It provides new lead abundance measurements in halo red giants, highlighting the minimal s-process contribution and reinforcing the r-process as the main source of lead in these stars.

Findings

[Pb/Fe] averages -0.3, no increase with metallicity

[Pb/Eu] averages -0.6, indicating r-process dominance

Little s-process contribution to lead in studied stars

Abstract

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