BROAD EMISSION-LINE OVI PLANETARY-NEBULAE NUCLEI

We present a study of broad-line O VI planetary nebulae nuclei (NGC 24 52, NGC 5189, NGC 6905, NGC 7026, and IC 2003) in which we use the neb ulae to derive the physical parameters of the central stars. From the study of the emission lines and the stellar continua we derive the eff ective temperatures and the luminosities of the stars, plasma characte ristics and (limited) abundances. By locating the stars on the HR diag ram we infer their evolutionary stages. We find that the O vr strength correlates with stellar luminosity, both for the broad-line and for t he narrow-line O VI stars. By comparing observational data to theoreti cal results, we find good agreement between the observed pulsational p eriods and effective temperatures and those obtained with C-O pre-whit e dwarf models.