Ultraviolet spectra of planetary nebulae. IX. High-dispersion observations of NGC 7662.

Abstract

High-dispersion IUE spectra of NGC 7662 have been obtained with exposure times optimized for measurement of the relative strengths of the components of: CIV lambda-lambda 1548, 1551; the forbidden line CIII lambda-lambda 1907, 1909 and the forbidden line Ne IV lambda-lambda 2422, 2424. The CIV ratio (lambda 1548)/(lambda 1551) is expected to be 2.00, the ratio of the statistical weights of the emitting levels, and the observed value is within 0.15 of 1.92. The forbidden line CIII and the forbidden line Ne IV ratios depend upon the electron density, Ne, and from the observations it is concluded that Ne for NGC 7662 is in the range 1300 to 5000/cu cm. The presence of the dielectronic recombination line CIII lambda 2297 is established beyond doubt. The absolute calibration of IUE high-dispersion spectra is also discussed.