Abstract
We present results from new IUE high-dispersion and archival low-dispersion spectra of NGC 6905. Ultraviolet emission lines of O VIII and possibly O VII are detected for the first time in NGC 6905. High-excitation lines of C IV, C V, O VI, [Mg V], [Ne III], [Ne IV], [Ne V], [Ar IV], and [Ar V] are also observed. Electron densities and terminal wind velocities are presented. Terminal wind velocities from O V and C IV lines are discussed. Variability (up to ≈25%) of the complex split He II λ1640 emission may be intrinsic or a function of position angle of the IUE camera entrance aperture. After reextracting the low-dispersion data, no significant changes between 1981 and 1991 were found for the strong O V λ1371, C IV λ1549, He II λ1640, and C III] λ1909 emissions. Many weak features not detected before have been identified in the archival low-resolution data. Some comparisons are made with UV spectra of Sand 3 and KPD 0005 + 6501. Preliminary results indicate O vm emissions in IUE spectra of NGC 2371–2, NGC 2867, NGC 5189, and NGC 5315, suggesting that these planetary nebulae, together with NGC 6905, RX λ2117 + 3412, and Sand 3, form a new "O VIII sequence." The present work illustrates the need to reexamine older IUE spectra and demonstrates that today's improved data analysis is capable of improving greatly the results reported in earlier publications.