IUE observations of the extreme B1 supergiant zeta ¹ Sco.

Abstract

High-resolution (delta lambda approximately 0.2 A) and low-resolution (delta lambda approximately 6 A) spectrograms in the wavelength range from about 1200 to 3200 A have been obtained using the IUE satellite. The high-dispersion spectrograms have been used to compile lists of the stellar and interstellar absorption lines and to derive accurate wavelength values for the identified stellar lines (using the interstellar lines for wavelength calibration). The stellar UV spectrum was found to be dominated by strong blueshifted absorption lines of resonance transitions and transitions from metastable lower states of the Fe III and Ni III ions. It is suggested that these ions play a major role in the mass loss mechanism of luminous early B stars. From the low-dispersion spectrograms the UV continuum energy distribution is derived, along with values for the effective temperature (approximately 19,000 K), the bolometric luminosity (about -10.35), the stellar radius (approximately 96 solar radii), and the likely stellar mass (about 65 solar masses).