Abundances in planetary nebulae: NGC 2792

Abstract

The mid-infrared spectrum of the rather circular planetary nebula NGC2792 taken with the Spitzer Space Telescope is presented. This spectrum is combined with the ultraviolet IUE spectrum and with the spectrum in the visual wavelength region to obtain a complete, extinction corrected, spectrum. The chemical composition of the nebula is then calculated in two ways. First by directly calculating and adding individual ion abundances, and secondly by building a model nebula that attempts to reproduce the observed spectrum. Because it is now possible to include the nebular temperature gradient, the chemical composition is more accurate than has been given earlier in the literature. Discussion of both the central star and the evolution of the star-nebula is then given