Ultraviolet Ionization Stratification in Wolf-Rayet Winds

Abstract

Ionization stratification can be used to study the structure of WR winds. In an accelerated outflow the stratification is observable through the Doppler effect as an inverse correlation of ionization potential (IP) with line width (FWHM). However, not only the average line widths of different ions, but also the line widths of one series of HeII show stratification. The evidence of both effects is demonstrated here as a part of ongoing study. The ultraviolet spectra of WR stars obtained from the IUE archive are used to get the IP vs FWHM diagrams as well as the principal quantum number n of HeII (n-3) transitions vs FWHM velocity relations. A systematic insight into stratification in HeII lines is provided on the basis of observations.