Ultraviolet spectroscopy of the extreme B supergiants P Cygni and zeta ¹ Scorpii.

Abstract

High-dispersion IUE spectra of P Cyg and Zeta-1 Sco are presented. Both show extreme line blanketing by Fe III and similar ions, formed in a low-velocity stellar wind. P Cygni also shows the same phenomenon in Fe II, at somewhat higher velocity, and appears to be cooler and less reddened then its visible spectrum suggests. Both stars show weak evidence for wind velocities up to about 400 km/s, but do not have high-velocity winds typical of OB supergiants. The interstellar extinction is discussed for each star, and their fundamental parameters estimated and compared.