THE WC10 CENTRAL STARS CPD-56-DEGREES-8032 AND HE-2-113 - III - WIND ELECTRON TEMPERATURES AND ABUNDANCES

We present a direct spectroscopic measurement of the wind electron tem peratures and a determination of the stellar wind abundances of the WC 10 central stars of planetary nebulae CPD-56 degrees 8032 and He2-113, for which high-resolution (0.15-Angstrom) UCLES echelle spectra have been obtained using the 3.9-m Anglo-Australian Telescope. The intensit ies of dielectronic recombination lines, originating from autoionizing resonance states situated in the C2++e(-) continuum, are sensitive to the electron temperature through the populations of these states, whi ch are close to their LTE values. The high-resolution spectra allow th e intensities of fine-structure components of the dielectronic multipl ets to be measured. New atomic data for the autoionization and radiati ve transition probabilities of the resonance states are presented, and used to derive wind electron temperatures in the two stars of 21 300 K for CPD - 56 degrees 8032 and 16 400 K for He 2-113. One of the diel ectronic lines is shown to have an autoionization width in agreement w ith the theoretical predictions. Wind abundances of carbon with respec t to helium are determined from bound-bound recombination Lines, and a re found to be C/He=0.44 for CPD-56 degrees 8032 and C/He=0.29 for He2 -113 (by number). The oxygen abundances are determined to be O/He=0.24 for CPD - 56 degrees 8032 and 0.26 for He 2-113. The effect of optica l depth on the temperature and abundance determinations is investigate d by means of a Sobolev escape-probability model. We conclude that the optically thicker recombination lines can still be used for abundance determinations, provided that their upper levels are far from LTE.