Physical conditions and abundances of CNO elements in NGC 7027.

Abstract

Spectroscopic observations of NGC 7027 have been obtained with the IUE satellite. The data have been used to investigate the nature of the extinction toward the object, recognizing the existence of three components due to: (1) interstellar, (2) local, and (3) internal dust. The physical conditions in the O III zone have been determined by analyzing lines all produced only by this ion. The observed lines of C IV, semiforbidden C III, semiforbidden O III, semiforbidden N III, semiforbidden N IV have been used for a determination of the abundances of the CNO elements more reliable than those made so far. C/H equals 0.0013, N/H equals 0.00033, O/H equals 0.00042 are obtained. The large overabundances of C and N relative to the solar values indicate that the nebular material was enriched by products of both CNO cycle and 3 - alpha process.