We show that a strong P-Cygni feature seen in the far-UV spectra of some very hot ( \mbox { $T _ { eff } $ } \gtrsim 85 kK ) central stars of planetary nebulae ( CSPN ) , which has been previously identified as C iii \lambda 977 , actually originates from Ne vii \lambda 973 .
Using stellar atmospheres models , we reproduce this feature seen in the spectra of two [ WR ] -PG 1159 type CSPN , Abell 78 and NGC 2371 , and in one PG 1159 CSPN , K 1-16 .
In the latter case , our analysis suggests an enhanced neon abundance .
Strong neon features in CSPN spectra are important because an overabundance of this element is indicative of processed material that has been dredged up to the surface from the inter-shell region in the ‘ ‘ born-again ’ ’ scenario , an explanation of hydrogen-deficient CSPN .
Our modeling indicates the Ne vii \lambda 973 wind feature may be used to discern enhanced neon abundances for stars showing an unsaturated P-Cygni profile , such as some PG 1159 stars .
We explore the potential of this strong feature as a wind diagnostic in stellar atmospheres analyses for evolved objects .
For the [ WR ] -PG 1159 objects , the line is present as a P-Cygni line for \mbox { $T _ { eff } $ } \gtrsim 85 kK , and becomes strong for 100 \lesssim \mbox { $T _ { eff } $ } \lesssim 155 kK when the neon abundance is solar , and can be significantly strong beyond this range for higher neon abundances .
When unsaturated , i.e . , for very high T _ { eff } and/or very low mass-loss rates , it is sensitive to \dot { M } and very sensitive to the neon abundance .
The Ne vii classification is consistent with recent identification of this line seen in absorption in many PG 1159 spectra .