The stellar winds of 203 Galactic O stars - A quantitative ultraviolet survey

Measurements of the resonance lines of C IV, N V, and Si IV in a sample of 203 O stars observed using IUE in a high-resolution mode are presented. The data are discussed using a consistent set of radius, luminosity, and mass estimates. The ratio of the maximum observed velocity and the terminal (farfield) velocity is found to average at 3.0 for 131 stars with strong or saturated lines, and at 2.6 for all stars. An expression is given which is the best available predictor of O star mass loss rates, giving an accuracy better than a factor of two irrespective of luminosity class. The ionization fractions C(3+)/C and N(4+)/N are found to be independent of stellar effective temperature, but increase by a factor of about two from main sequence stars to supergiants. Two new possible ON stars are identified, and enhanced surface nitrogen abundance is confimed in ON stars. Discrete narrow absorption features are found to be virtually universal characteristic of O star P Cygni profiles.