An O VIII Sequence for Planetary Nebula Nuclei

Abstract

The detection of O VIII emission lines in ultraviolet and optical spectra of high-excitation planetary nebula central stars suggests an "O VIII Sequence" for these object. Emission lines of O VII are also detected. Seven out of ten central stars for these planetaries are known to be nonradial g-mode pulsators. The stars form a narrow strip when plotted on the log L*/L_sun - log Teff H-R diagram. (SECTION: Stars)