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Published online by Cambridge University Press: 14 August 2015
The first results are presented of an extensive spectroscopic study of HD 77581 = Vela X-1, based on several averaged Coude spectra. The profile of Hβ is phase-dependent and consists of two absorption components superimposed on one another. The profile of He II 4686 A is of the P-Cygni type around phase 0.7, whereas the line is in absorption with variable strength between phase 0.9 and phase 0.5 (with respect to the X-ray eclipse).