2000A&A...361..231B

During 25 nights distributed between September 1996 and September 1997, a programme of intensive spectroscopy of the SMC WR binary HD 5980 was conducted, providing a series of 116 high-resolution (R=60000) profiles of the HeII λ4686 emission line. These observations were complemented with 9 additional spectra obtained: 5 in October-November 1998 and 4 in January 1999, with a resolving power of R=48000. This observational material has allowed to investigate, as a function of the orbital phase, the variations of the line equivalent width, of the full line width at half-maximum, and of the line radial velocity, over many different orbits. The discovery, on one night, of a profile oscillation at the red side of the emission, on a timescale of ∼7 hours, is reported. Though revealing a rather complex phase-dependent behaviour of the HeII λ4686 line, the analysis of the present data still favours the hypothesis that in HD 5980 this highly variable emission feature does not characterize a genuine WR star, but arises instead in a wind-wind collision shock zone.