2002MNRAS.333..347N

We present a study of optical spectra of the Wolf-Rayet star AzV 336a (=SMC WR7) in the Small Magellanic Cloud. Our study is based on data obtained at several Observatories between 1988 and 2001. We find SMC WR7 to be a double-lined WN+O6 spectroscopic binary with an orbital period of 19.56d. The radial velocities of the He absorption lines of the O6 component and the strong Heii emission at λ 4686Å of the WN component describe anti-phased orbital motions. However, they show a small phase shift of ∼1d. We discuss possible explanations for this phase shift. The amplitude of the radial velocity variations of Heii emission is twice that of the absorption lines. The binary components have fairly high minimum masses, ∼18 and 34M_☉ for the WN and O6 components, respectively.