WIND-WIND INTERACTION IN THE CLOSE WOLF-RAYET BINARY CQ CEPHEI (WN6-IB)(09 II)

A large collection of blue and yellow CCD spectra of the short-period eclipsing binary CQ Cep allows us to improve the double-line (SB2) orb it of Kartasheva and Snezhko and reclassify the system as WN6+O9 II-Ib . With orbital inclination i = 78 degrees-65 degrees, the masses and r adii are M(O) = 18-23 M(.), M(WR) = 15-19 M(.), R(O) less than or equa l to 10 R(.), 2 R(.) less than or equal to R(WR) less than or equal to 10 R(.). For its spectral type, the O star mass and radius are smalle r than values deduced from evolutionary models but agree with recent d eterminations of other O stars in binaries. The W-R star is shown to c ontain a small amount of hydrogen in its wind. Because of the rapid or bit revolution compared to the wind velocities, the wind interaction z one is tightly wrapped around the system. We construct a phenomenologi cal model which explains the numerous phase-dependent spectral variati ons.