P93	September 2004

¹ Institut d'Astrophysique et de Géophysique - Université de Liège, Allée du 6 Août, Bât B5c, B-4000 Liège (Sart Tilman), Belgium

^* Research Associate FNRS, Belgium
^** Research Director FNRS, Belgium

⁺ Based on observations collected at the Observatoire de Haute Provence, France.

Abstract

     We present the results of a spectroscopic campaign revealing that the non-thermal radio emitter CygOB2 #8A is an O6 + O5.5 binary system. We propose the very first orbital solution indicating a period of about 21.9 days. The system appears to be eccentric (0.24 +/- 0.04) and is likely seen under a rather low inclination angle. The mass ratio of the components is close to unity. The impact of the binarity of this star in the framework of our understanding of non-thermal radio emission from early-type stars is briefly discussed.