On the Problem of the Chemical Composition of β Lyrae

Abstract

Two determinations of helium abundance in the primary β Lyrae's component existed before 1975. According to Boyarchuk (1959) helium is 631 times overabundant relative to hydrogen and according to Hack and Job (1965) the ratio He/H varies from 1 to 2.25 depending on the effective temperature. We started to examine this probleme with the aim to decide between these extreme results. In the meantime there were published two papers by Leushin at al. (1977, 1979) in which there was found, that He/H = 1.5 for Teff = 12 000 °K and log g = 2.5. The earlier results were based on equivalent widths analysis with curve of growth method. The authors of newly published papers have started from convenient models of the atmosphere, calculated equivalent widths and compared them with observation. In our paper (Bahýl′ 1979) we started from models of the atmosphere, too. Then we calculated the theoretical profiles. We have found the best fit for the model Böhm-Vitense (1967), Teff = 12 900 °K, log g = 2 and He/H = 2.72, as shown in Fig. 1.