Properties of Hot, Massive Stars: The Impact of FUSE

Abstract

The impact of FUSE upon the fundamental parameters of OB stars and Wolf-Rayet stars is reviewed. The stellar wind signatures available in the far-UV provide us with important additional diagnostics of effective temperature. Together with improved non-LTE stellar atmosphere models allowing for line blanketing and stellar winds, this has led to a downward revision in the spectral type-temperature calibration for O stars versus Vacca et al. (1996) In addition, the Lyman continuum ionizing fluxes from O dwarfs are compared with previous calibrations of Panagia (1973) and Vacca et al. We also discuss mass-loss rates in OB stars, such that agreement between recent theoretical predictions (Vink et al. 2000, 2001) and observations of O supergiants is possible, solely if winds are clumped in the far-UV and H-alpha line forming regions, as favoured by line profile comparisons for PV 1118-28 (early to mid O) or SIV 1062-1073 (late O to early B) in FUSE datasets. In contrast, B supergiant wind strengths are predicted to be much higher than observations indicates, especially if their winds are also clumped. Finally, significant upward revisions in wind velocities of very late WN stars are indicated by NII 1085 resonance line observations, plus elemental abundances in OB and WR stars are briefly discussed.