The rocket-ultraviolet spectrum of the planetary nebula NGC 7027

An ultraviolet spectrum of NGC 7027 was obtained with a rocket-borne telescope. The observed fluxes are given on an absolute basis, and upper limits are given for the strongest predicted lines which were not observed. The extinction correction was made on the basis of the observed and calculated line ratios for the hydrogenic recombination line of He ii at 1640 A to H$beta$. The extinction is in agreement with ground-based determinations. When corrected for extinction, the C iv resonance line at 1549 A is in good agreement with the intensity calculated from models, but the C iii intercombination line at 1909 A is a factor of 10 too bright. The addition of dielectronic recombination to the models sufficiently changes the C iii concentration to reduce the discrepancy to a factor of 4. The abundance of carbon is assumed to 2x10$sup -4$ that of hydrogen. Using carbon abundances for the Sun, which are up to 3 times higher, this discrepancy disappears, and there must be attenuation in the C iv line. Since the optical depth is approx.10$sup 4$ at the line center, no appreciable number of absorbing grains can exist in the C iv-producing region of the nebula. (AIP)