Abundances in planetary nebulae: NGC 6826

Abstract

Aims: We determine the chemical abundances and other parameters of the nebula NGC 6826 and its central star.
Methods: We present new ISO spectra and combine them with archival IUE and optical spectra from the literature to get 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 second by building a model nebula that will reproduce the observed spectrum.
Results: The results of these two methods are compared. In addition, we discuss the star exciting the nebula.

Based

on observations with ISO, an ESA project with instruments funded

by ESA Member States (especially the PI countries: France,

Germany, The Netherlands, and the UK) and with the

participation of ISAS and NASA.