On the Baldwin effect of HeII emission lines in WR (WN) stars

We investigate the relation between the equivalent width of He II emission lines and the monochromatic continuum luminosity at the line wavelength in the spectra of Wolf-Rayet stars. Model stellar atmospheres and spectra are used to show that the equivalent width inversely correlates with the monoch romatic continuum luminosity. We find the effect in Wolf-Rayet star models over a large range of stellar parameters. The effect is shown to be connect ed to density differences among Wolf-Rayet star winds. The conclusion is dr awn that the Baldwin effect may provide a new method for the determination of Wolf-Rayet star distances.