THE SPECTRUM OF THE PLANETARY NEBULA NGC 6790

Abstract

ABSTRACT International Ultraviolet Explorer (IUE) and optical region spectroscopic observations are presented for the medium excitation planetary nebula (PN), NGC 6790, which displays a rich spectrum permitting application of several diagnostic ratios and the calculation of a number of ionic concentrations, Nion/N(H+). NGC 6790 seems to be a relatively young object which may represent a stage of development only slightly beyond that of a PN such as Hb 12. The diagnostics for NGC 6790 suggest a rather large density range, although not one as great as that found in IC 4997. An attempt is made to calculate a plausible simple spherically symmetrical model. We suggest that NGC 6790 may serve as a prototype "standard" for PN of intermediate age, density, and evolutionary development. Further modeling attempts would appear inappropriate until images of high spatial resolution become available.