2013A&A...549A..65L

We present the high-dispersion spectra of the elliptical ring shaped planetary nebula NGC 6803, secured with the Hamilton Echelle Spectrograph attached to the 3-m Shane telescope of Lick Observatory. Numerous lines from neutral to quadruply ionized ions are presented in the wavelength region from 3650 to 9900Å. We also use the low dispersion UV spectral data obtained with the 60-cm interstellar ultraviolet explorer. In spite of its simplistic symmetrical bilateral shape, the diagnostics imply that the physical condition of the nebular shell is very complex with a huge density range of 1300-80000cm^–3. A comparison of the 1995 and 2001 [ArIV] data suggests that the density increase occurred near the inner shell boundary. In spite of a huge ionization potential range, the average electron temperature indicated by primary diagnostic lines is relatively low, i.e., T_e≤9500K, except for [ClIV], from which we derive a temperature that is around 11500 K. We derived the chemical abundances of He, C, N, O, Ne, S, Ar, Cl, and K, based on the physical condition suggested by diagnostics and photo-ionization analysis. The chemical abundances of NGC 6803 are mostly enhanced when compared with the average Galactic planetary nebula. The effective temperature of its central star appears to be about 90000 K and its luminosity about 2400L_☉, assuming a distance of 3000pc. The evolutionary track implies that NGC 6803 might have been evolved from a companion star of about 1.0M_☉ in a binary system, or from a single progenitor of about 1.5M_☉, born in a metal-rich zone near the Galactic plane.