Radiation-driven winds of hot luminous stars. XII. A first step towards detailed UV-line diagnostics of O-stars.

Improved radiation driven wind models are constructed to calculate detailed synthetic UV spectra of hot luminous stars. The model improvements comprise: a very detailed multilevel non-local thermodynamic equilibrium (NLTE) treatment of 29 of the most important ionization stages, in particular C, N, O and Fe using accurate atomic data; the approximate inclusion of EUV radiation by shock heated matter in the ionization rates and a simple simulation of photospheric line blocking. The direct ionization by EUV shock radiation has important effects on the lines of the highest ionization stages, whereas line blocking is needed to reproduce the lowest stages of ionization that are observed. A detailed comparison between observed and calculated synthetic spectra of two O-stars, zeta Puppis in the Galaxy and Melnick 42 in the LMC, has been carried out.