We analysed UV FUSE , IUE , and HST/STIS spectra of five of the hottest [ WCE ] -type central stars of planetary nebulae : NGC 2867 , NGC 5189 , NGC 6905 , Pb 6 , and Sand 3 .
The analysis leveraged on our grid of CMFGEN synthetic spectra , which covers the parameter regime of hydrogen deficient central stars of planetary nebulae and allows a uniform and systematic study of the stellar spectra .
The stellar atmosphere models calculated by us include many elements and ionic species neglected in previous analyses , which allowed us to improve the fits to the observed spectra considerably and provided an additional diagnostic line : the Ne vii \lambda 973 \mathrm { \AA } , which had not been modelled in [ WCE ] spectra and which presents , in these stars , a strong P-Cygni profile .

We report newly derived photospheric and wind parameters and elemental abundances .
The central stars of NGC 2867 , NGC 5189 , and Pb 6 had their temperatures revised upward in comparison with previous investigations and we found the carbon to helium mass ratio of the sample objects to span a wide range of values , 0.42 < C:He < 1.96 .
Modelling of the Ne vii \lambda 973 \mathrm { \AA } P-Cygni profile indicated strong neon overabundances for the central stars of NGC 2867 , NGC 5189 , NGC 6905 , and Pb 6 , with Ne mass fractions between 0.01 and 0.04 .
Nitrogen abundances derived by us for the central stars of NGC 5189 , Pb 6 , and Sand 3 are higher than previous determinations by factors of 3 , 10 , and 14 , respectively .