C-IV AND O-VI TRANSITIONS IN THE REGION LAMBDA-LAMBDA-1100-2000 AND EXAMPLES FOUND IN IUE SPECTRA OF HOT STARS

We present Ritz wavelengths for more than 130 transitions of C IV and O VI in the range lambda lambda 1100-2000 and show examples of absorption features as seen in representative examples of high-dispersion IUE spectra of very hot (similar to 100,000 K) nuclei of planetary nebulae, white dwarfs, and PG 1159-type stars. The regions near He II lambda 1640 and interstellar Si II lambda 1260 are of particular interest because they coincide with strong C IV and O VI transitions. O VI absorptions are detected in the IUE spectrum of the nucleus of the planetary nebula NGC 7293, which suggests that this object may be a ''hybrid'' star with an H-rich atmosphere.