ABUNDANCE ANALYSIS OF THE SLOW NOVA PW-VULPECULAE-1984

We determine the elemental abundances for the ejecta of the slow nova PW Vul 1984. Our technique uses a minimization of the emission-line fi ts of a photoionization model to available ultraviolet, optical and in frared spectra. We find the following abundances (by number) with resp ect to solar: He/H=1.0+/-0.4, C/H=7.0(-4)(+7), N/H=85(-41)(+59) and O/ H=6(-2)(+7). In addition, there is weak evidence for solar Ne and Mg, and for twice solar Fe. Previous studies of PW Vul by Saizar et al. an d Andrea et al. yielded considerable differences in their derived elem ental abundances for the ejecta. Our abundances fall in between those found in the previous studies. To explain the discrepant abundances, w e analyse in detail the data and methods used to obtain the previous r esults. The abundances found by Saizar et al. are significantly smalle r than our values because of the lower electron temperature used by th em in deriving elemental abundances from ion abundances. Andrea et al. used an ionization correction method to obtain their abundances and l ater verified their results with a photoionization model. Our analysis of their data shows that the absolute fluxes of the optical emission lines used by Andrea et al. are underestimated by 15 per cent, leading to a factor of 2 increase in their derived abundances. We also find t hat the photoionization model used by Andrea et al. predicts twice as much carbon as the photoionization code we used even when fitting the same data with similar model parameters.