Discovery of Enhanced Germanium Abundances in Planetary Nebulae with the Far Ultraviolet Spectroscopic Explorer

We report the discovery of Ge III λ1088.46 in the planetary nebulae (PNe) SwSt 1, BD+303639, NGC 3132, and IC 4593, observed with the Far Ultraviolet Spectroscopic Explorer. This is the first astronomical detection of this line and the first measurement of Ge (Z = 32) in PNe. We estimate Ge abundances using S and Fe as reference elements, for a range of assumptions about gas-phase depletions. The results indicate that Ge, which is synthesized in the initial steps of the s-process and therefore can be self-enriched in PNe, is enhanced by factors of ≥ 3 – 10. The strongest evidence for enrichment is seen for PNe with Wolf-Rayet central stars, which are likely to contain heavily processed material. Subject headings: line: identification—planetary nebulae: general—planetary nebulae: individual (BD+303639, SwSt 1, IC 4593, NGC 3132)—stars: AGB and post-AGB— nucleosynthesis, abundances—ultraviolet: ISM