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Context: The commonly accepted mass-luminosity relation of central stars ofplanetary nebulae (CSPNs) might not be universally valid. While earlier opticalanalyses could not derive masses and luminosities independently (instead takingthem from theoretical evolutionary models) hydrodynamically consistentmodelling of the stellar winds allows using fits to the UV spectra toconsistently determine also stellar radii, masses, and luminosities withoutassuming a mass-luminosity relation. Recent application to a sample of CSPNsraised questions regarding the validity of the theoretical mass-luminosityrelation of CSPNs.  Aims: The results of the earlier UV analysis are reassessed by means of asimultaneous comparison of observed optical and UV spectra with correspondingsynthetic spectra.  Methods: Using published stellar parameters (a) from a consistent UV analysisand (b) from fits to optical H and He lines, we calculate simultaneous opticaland UV spectra with our model atmosphere code, which has been improved byimplementing Stark broadening for H and He lines.  Results: Spectra computed with the parameter sets from the UV analysis yieldgood agreement to the observations, but spectra computed with the stellarparameters from the published optical analysis and using correspondingconsistent wind parameters show large discrepancies to both the observedoptical and UV spectra. The published optical analyses give good fits to theobserved spectrum only because the wind parameters assumed in these analysesare inconsistent with their stellar parameters. By enforcing consistencybetween stellar and wind parameters, stellar parameters are obtained whichdisagree with the core-mass-luminosity relation for the objects analyzed. Thisdisagreement is also evident from a completely different approach: aninvestigation of the dynamical wind parameters.

astronomy and astrophysics

Radiation-driven winds of hot luminous stars XVII. Parameters of  selected central stars of PN from consistent optical and UV spectral analysis  and the universality of the mass-luminosity relation