2010ApJ...719L..32W

Up to now, iron had not been found in any hydrogen-deficient (pre-) white dwarf of spectral type PG1159, despite intense searching in a number of objects. Consequently, an iron deficiency was claimed, in some cases at least 1 dex. The primary indicators were UV lines of Fe VII. Therefore, the search was confined to relatively cool PG1159 stars (T_eff≲150,000 K), otherwise Fe is too strongly ionized for a significant population of Fe VII. In this Letter, we announce the discovery of iron in the very hottest PG1159 stars (T_eff= 150,000-200,000 K; RX J2117.1+3412, K 1-16, Longmore 4, NGC 246, H1504+65), based on the identification of the Fe X λλ979.3, 1022.9 lines in spectra obtained with the Far Ultraviolet Spectroscopic Explorer. Surprisingly, our analysis results in a solar iron abundance for these stars. It is conspicuous that they are among the most massive PG1159 stars (0.71-0.82 M_☉), in contrast to those objects for which strongest Fe deficiency was claimed (0.53-0.56 M_☉).