The WC10 central stars CPD-56 deg8032 and He2-113 - II. Model analysis and comparison with nebular properties

We present detailed atmospheric analyses of two [WC10] central stars of planetary nebulae (PNe), CPD-56 deg8032 and He2-113, the results of which are compared with parameters inferred from their nebular properties. Our quantitative study is based on non-LTE modelling of diagnostic Hei-II, CII-IV and OII-III lines. We find that spectroscopic similarities are reflected in the derived stellar properties: for both stars we obtain T_eff~30 kK and log L/Lsolar=3.7 log (/M/Msolar yr^-1)=-5.4 and v_∞=225 km s^-1 for CPD-56 deg8032, while log (/M/Msolar yr^-1)=-6.1 and v_∞=160 km s^-1 for He2-113. The derived stellar properties are fairly consistent with the recent study of Leuenhagen et al., when adjusted for the different distances adopted. We find excellent agreement between our C^2+ wind temperature and the independent determination by De Marco et al., supporting our assumption of radiative equilibrium. We find that both stars are highly enriched in carbon and oxygen, but with stellar hydrogen undetectable for He2-113 (in contrast to Leuenhagen et al.). Our final abundance determinations indicate H:He:C:O mass fractions of 0:34:52:14 for CPD-56 deg8032 and 0:34:54:13 for He2-113. We confront our model flux distributions with observed nebular properties using Zanstra and photoionization techniques, and identify a major discrepancy between the observed and predicted nebular properties for these particular PNe. The hydrogen ionizing fluxes predicted by our WR non-LTE models greatly exceed those implied by nebular observations. The lack of heavy-element line blanketing in our wind models could be responsible. However, the geometry and high nebular densities of these PNe suggest that they represent poor probes of the Lyman continuum flux of their central stars.