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Summary and Future Work

We have presented the status of our hydrodynamic non-LTE models for expanding atmospheres, where accurate atomic data, the EUV and X-ray radiation from shock-heated matter, and a consistent calculation of line blocking and blanketing are treated.

That this effort is worthwhile has already been demonstrated by the quantitative spectroscopic analyses of seven O stars. Nevertheless, we still have to show that the realistic models from our improved method also lead to improvements in detailed spectrum synthesis, or whether refinements to the method are still required. In addition, we need to establish whether the discrepancies between observed and theoretically predicted wind-momentum rates, which appear to exist for O stars (cf. Puls et al. 1996), can be removed by means of our new models. Furthermore, we still have to investigate the impact of our new ionizing fluxes on the quantitative analysis of emission-line spectra of HIIregions and planetary nebulae.

This research was supported by the DFG in the `Gerhard Hess Programm' under grant Pa 477/1-3.

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Gies: What difference does line-blanketing make to the effective temperature you would estimate for a given stars?

Pauldrach: It depends whether you have a dwarf or a supergiant; in the case of a 50kK supergiant it's about 12% in the flux, which I would say corresponds to 4-5kK.

Gies: How does this relate to the wind blanketing discussed by Abbott & Hummer?

Pauldrach: The effect I showed is due to wind blanketing, and not photospheric line blanketing.

Crowther: Your models seem to be in line with the Kurucz model distributions in terms of ionizing fluxes for the very hot O stars, whereas I thought Daniel Schaerer and Alex de Koter got quite large differences?

Pauldrach: I think this is the case, but perhaps Schaerer should comment?

Schaerer: I will discuss this when I give my talk tomorrow.

Kudritzki: Could you say something about the effect of shocks in the wind?

Pauldrach: Yes, we include shocks but I didn't have time to discuss this. We use an approximate description of the emission coefficient, using a filling factor and a cooling function for the shocks. So we have two free parameters: a filling factor (which is fixed by an integration over the emergent flux in Rosat observations), and the jump velocity, which determines the immediate post-shock temperature and hence the cooling function. For the jump velocity we found a proportionality to the terminal velocity. As an example, the model for  Pup fits the ROSAT observation very well.