Optical spectroscopy of X-Mega targets - II. The massive double-lined O-type binary HD 93205

A new high-quality set of orbital parameters for the O-type spectroscopic b inary HD 93205 has been obtained combining echelle and coude CCD observatio ns. The radial velocity orbits derived from the He II lambda 4686 Angstrom (primary component) and Hei lambda 4471 Angstrom (secondary component) abso rption lines yield semi-amplitudes of 133 +/- 2 and 314 +/- 2 km s(-1) for each binary component, resulting in minimum masses of 31 and 13 M-. (q = 0. 42). We also confirm for the binary components the spectral classification of O3 V + O8 V previously assigned. Assuming for the O8 V component a 'norm al' mass of 22-25 M-. we would derive for the primary O3 Va mass of 'only' 52-60 M-. and an inclination of about 55 degrees for the orbital plane. We have also determined for the first time a period of apsidal motion for this system, namely 185 +/- 16 yr using all available radial velocity data sets of HD 93205 (from 1975 to 1999). Phase-locked variations of the X-ray emis sion of HD 93205 consisting of a rise of the observed X-ray flux near peria stron passage are also discussed.