Abstract
We have obtained a series of high dispersion IUE observations in the short and long wavelength ranges, with different exposure times in order to measure both intense and weak emission line fluxes. Several density dependent line ratios of different ions (SII,CIII,NIII, SiIII, N IV and 0 IV) have been measured and the results confirm that the nebula has no systematic density variations. The collisionally excited lines of [Mg V] λλ2783, 2928 are present but no measurable Mg II λλ2795, 2803 appear in emission. The derived ionic abundances show a depletion of a factor of %3 of the gaseous magnesium in the external part of the nebula. Expansion velocities for different ions have been obtained and we find an increasing expansion velocity with decreasing ionization degree. We have derived a vexp vs radius relation which is compatible with the predictions of models of isothermal expansion into vacuum. The kinematical age of tbe nebula is 3150 years which is indicative of a mean mass loss ratio of 4.8 x 10^-5 M⊙ year-1. A slight asymmetry has been found between the blue shifted and the red shifted component of the lines, which is wavelength dependent. From this dependence we find a dust optimal depth of τ(HB) = 0.08±0.04, within the ionized zone. The complete description of this work will appear in the Revistata Mexicana de Astronomia y Astrofisica, Volumen 11, 1985.
