A new calibration of stellar parameters of Galactic O stars
  We present new calibrations of stellar parameters of O stars at solar metallicity taking non-LTE, wind, and line-blanketing effects into account. Gravities and absolute visual magnitudes are derived from results of recent spectroscopic analyses. Two types of effective temperature scales are derived: one from a compilation based on recent spectroscopic studies of a sample of massive stars - the ``observational scale'' - and the other from direct interpolations on a grid of non-LTE spherically extended line-blanketed models computed with the code CMFGEN (Hillier & Miller 1998) - the ``theoretical scale''. These Teff scales are then further used together with the grid of models to calibrate other parameters (bolometric correction, luminosity, radius, spectroscopic mass and ionising fluxes) as a function of spectral type and luminosity class. Compared to the earlier calibrations of Vacca et al. (1996) the main results are: 1) the effective temperature scales are cooler by 2000 to 8000 K, the reduction being the largest for early supergiants; 2) bolometric corrections are lower by 0.1 mag for a given temperature, and are lower by 0.3 - 0.6 mag for a given spectral type; 3) luminosities are reduced by 0.20 to 0.35 dex; 4) Lyman ionising fluxes are lower by 0.20 to 0.80 dex. We provide calibration tables for each luminosity class and for both types of Teff scales. 
F. Martins, D. Schaerer, D.J. Hillier