Combined stellar structure and atmosphere models for massive stars: Revised ionising fluxes for O stars

We present the EUV fluxes derived from the recent "combined stellar structure and atmosphere models" (CoStar models). The atmosphere models in particular account for the stellar wind and include non-LTE effects and line blanketing. We provide an extensive set of calculations from tracks between 20 and 120 Msun at Z=0.02 (solar metallicity) and Z=0.004. They cover the entire parameter space of O3--B0 stars of all luminosity classes. Model uncertainties are discussed in the light of recent EUV and X-ray observations. We show the importance of using adequate O star ionising fluxes for the interpretation of HII regions, young starbursts and related objects.