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Paper: UV and FUV Spectroscopy of the Hybrid PG1159-Type Central Star of NGC7094
Volume: 391, Hydrogen-Deficient Stars
Page: 125
Authors: Ziegler, M.; Rauch, T.; Reiff, E.; Werner, K.; Kruk, J.W.; Oliveira, C.M.
Abstract: Previous studies aiming at the iron-abundance determination in three PG1159 stars (K1−16, PG1159−035, NGC7094) and a [WC]-PG1159 transition star (Abell 78) have revealed that no object shows any iron line in the UV spectrum. The stars are iron-deficient by at least 1 dex, typically. A possible explanation is that iron nuclei were transformed by neutron captures into heavier elements (s-process), however, the extent of the iron-destruction would be much stronger than predicted by AGB star models. But if n-captures are the right explanation, then we should observe an enrichment of trans-iron elements. In this paper we report on our search for a possible nickel overabundance in one of the four Fe deficient PG1159 stars, namely the central star NGC7094. We are unable to identify any nickel line in HST and FUSE spectra and conclude that Ni is not overabundant. It is conceivable that iron was transformed into even heavier elements, but their identification suffers from the lack of atomic data.
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