UV Spectrophotometry of the Hottest Stars from the Southern HK Survey

Abstract

Low-resolution UV spectra have been obtained with the long- and short-wavelength lUE cameras for seven of the hottest stars identified in the ongoing HK objective-prism/interference-filter survey begun by Beers, Preston, & Shectman. These stars are a subset of a sample of some 25,000 stars at high galactic latitude whose objective-prism spectra indicate that they are hotter than the Population II main-sequence turnoff in the magnitude range 11 ≤ B ≤ 15.5. The UV fluxes have been corrected for interstellar reddening using a standard reddening law, and comparison of the integrated fluxes in the two lUE cameras indicates that the effective temperatures of these stars range from 40,000 K to 80,000 K. The UV absorption spectra of six of the seven stars are characterized by a strong He II λ1640 line and 3-n series of He II. Five of these stars show strong C IV λ1550 absorption. The low-resolution UV spectrum of the remaining object is featureless.