Abstract. Spectral analysis of hot luminous stars requires adequate model atmospheres which take into account the effects of NLTE and radiation driven winds properly. Here we present significant improvements of our approach in constructing detailed atmospheric models and synthetic spectra for hot luminous stars. Moreover, as we regard our solution method in its present stage already as a standard procedure, we make our program package WMbasic available to the community (download is possible from the URL given below). The most important model improvements towards a realistic description of stationary wind models concern:(i) A sophisticated and consistent description of line blocking and blanketing. Our solution concept to this problem renders the line blocking influence on the ionizing fluxes emerging from the atmospheres of hot stars -mainly the spectral ranges of the EUV and the UV are affected -in identical quality as the synthetic high resolution spectra representing the observable region. In addition, the line blanketing effect is properly accounted for in the energy balance. (ii) The atomic data archive which has been improved and enhanced considerably, providing the basis for a detailed multilevel NLTE treatment of the metal ions (from C to Zn) and an adequate representation of line blocking and the radiative line acceleration. (iii) A revised inclusion of EUV and X-ray radiation produced by cooling zones which originate from the simulation of shock heated matter.This new tool not only provides an easy-to-use method for O-star diagnostics, whereby physical constraints on the properties of stellar winds, stellar parameters, and abundances can be obtained via a comparison of observed and synthetic spectra, but also allows the astrophysically important information about the ionizing fluxes of hot stars to be determined automatically. Results illustrating this are discussed by means of a basic model grid calculated for O-stars with solar metallicity. To further demonstrate the astrophysical potential of our new method, we first provide a detailed spectral diagnostic determination of the stellar parameters, the wind parameters, and the abundances by an exemplary application to one of our grid-stars, the O9.5Ia O-supergiant α Cam. Our abundance determinations of the light elements indicate that these deviate considerably from the solar values.

Abstract. This paper analyzes the inter-relation between line-statistics and radiative driving in massive stars with winds (excluding Wolf-Rayets) and provides insight into the qualitative behaviour of the well-known force-multiplier parameters k CAK , α and δ, with special emphasis on α.After recapitulating some basic properties of radiative line driving, the correspondence of the local exponent of (almost) arbitrary line-strength distribution functions and α, which is the ratio of optically thick to total line-force, is discussed. Both quantities are found to be roughly equal as long as the local exponent is not too steep.We compare the (conventional) parameterization applied in this paper with the so-calledQ-formalism introduced by Gayley (1995) and conclude that the latter can be applied alternatively in its most general form. Its "strongest form", however (requiring the AnsatzQ = Q o to be valid, with Q o the line-strength of the strongest line), is justified only under specific conditions, typically for Supergiants with T eff > ∼ 35 000 K.The central part of this paper considers the question concerning the shape of the line-strength distribution function, with line-strength k L as approximate depth independent ratio of line and Thomson opacity. Since k L depends on the product of oscillator strength, excitationand ionization fraction as well as on elemental abundance, all of these factors have their own, specific influence on the final result.At first, we investigate the case of hydrogenic ions, which can be treated analytically. We find that the exponent of the differential distribution is −4/3 corresponding to α = 2/3, as consequence of the underlying oscillator strength distribution. Furthermore, it is shown that for trace ions one stage below the major one (e.g., Hi in hot winds) the equality α+δ ≈ 1 is valid throughout the wind.For the majority of non-hydrogenic ions, we follow the statistical approach suggested by Allen (1966), refined in Send offprint requests to: J. Puls e-mail: uh101aw@usm.uni-muenchen.de a number of ways which allow, as a useful by-product, the validity of the underlying data bases to be checked. Per ion, it turns out that the typical line-strength distribution consists of two parts, where the first, steeper one is dominated by excitation effects and the second one follows the oscillator strength distribution of the specific ion.By summing up the contributions of all participating ions, this direct influence of the oscillator strength distribution almost vanishes. It turns out, however, that there is a second, indirect influence controlling the absolute line numbers and thus k CAK . From the actual numbers, we find an average exponent of order −1.2 . . . − 1.3, similar to the value for hydrogen.Most important for the shape of the total distribution is the difference in line-statistics between iron group and light ions as well as their different (mean) abundance. Since the former group comprises a large number of meta-stable levels, the line number from iron group elements is much...

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