The Fundamental Parameters of Massive Stars

We analyzed far-UV (FUSE), UV (HST,IUE) and optical spectra of hot massive stars in the Milky Way with non-LTE, line-blanketed models with sphericity and expanding winds. We were able to reconcile previously discrepant diagnostics from Ha to highly ionized transitions (e.g. OVI and NV) with a revised treatement of soft X-rays from shocks and clumping in the stellar wind. These effects could be constrained uniquely by combining lines in the FUSE range and at longer wavelenghs. We derived T sub(eff) and luminosity values lower than canonical values, and refined measurements of mass-loss rate. The T sub(eff) recalibration of O-type stars has relevant implications for our understanding of massive star evolution and energy balance of HII regions. Mass loss is a major source of uncertainty in our current knowledge of massive stars evolution, and a consistent derivation of mass-loss rate from optical and far-UV lines is an important step forward.