The near ultraviolet spectra of alf LYR and BET Ori.

The observed high resolution near-ultraviolet spectra of alpha Lyrae (A0 V) and beta Orionis (B8 Ia) are compared with theoretical spectra. The observations, taken with a balloon-borne spectrograph, are in the wavelength region 2730-2880 A and have a resolution of about 0.1 A. The spectrum of alpha Lyrae, consisting mainly of the lines of once-ionized magnesium, iron, and chromium, can be well described by a classic unblanketed LTE model atmosphere (effective temperature of 9500-10,000 K, a log g of 4.0, a microturbulence of 2 km/s, and a projected rotational velocity v sin i of 18-20 km/s). For beta Orionis, a reasonable fit between the observed and calculated spectra was obtained for an effective temperature of 11,000-12,000 K, log g = 2.0-2.5, v sin i = 35-40 km/s, and a microturbulence of 5 km/s. The blanketed models show too much surface cooling for both stars.