Metal abundances in PG1159 stars from Chandra and FUSE spectroscopy
  We investigate FUSE spectra of three PG1159 stars and do not find any evidence for iron lines. From a comparison with NLTE models we conclude a deficiency of 1-1.5 dex. We speculate that iron was transformed into heavier elements. A soft X-ray Chandra spectrum of the unique H- and He-deficient star H1504+65 is analyzed. We find high neon and magnesium abundances and confirm that H1504+65 is the bare core of either a C-O or a O-Ne-Mg white dwarf. 
K. Werner, J.L. Deetjen, S. Dreizler, T. Rauch, M.A. Barstow, J.W.   Kruk