Temperatures of Central Stars of Planetary Nebulae

A method is proposed for the investigation of the ultraviolet spectrum of the nuclei of planetary nebulae in the interval 912–90 Å. It is based on the data for the relative dimensions of [Ne V ], He II and H I luminosity zones in the nebulae. The optical thicknesses of the nebulae for L c radiation of hydrogen have been estimated from the intensities of the [O I ] λλ 6300–6364 lines. The ultraviolet spectra are obtained for six planetary nebulae; in the spectral interval mentioned they appear to be similar to black-body spectra. The colour temperatures of the nuclei are determined too; all of them are in the range 100 000° to 200 000°K, and are higher than appropriate Zanstra temperatures. The linear radii of the nuclei are also estimated.