Magellanic Cloud WC/WO Wolf-Rayet stars - II. Colliding winds in binaries

A search for evidence of colliding winds is undertaken among the four certa in Magellanic Cloud WC/WO spectroscopic binaries found in the companion Pap er I, as well as among two Galactic WC/WO binaries of very similar subtype. Two methods of analysis, which allow the determination of orbital inclinat ion and parameters relating to the shock cone from spectroscopic studies of colliding winds, are attempted. In the first method, Luhrs' spectroscopic model is fitted to the moderately strong C III 5696-Angstrom excess line em ission arising in the shock cone for the stars Br22 and WR 9. The four othe r systems show only very weak C III 5696-Angstrom emission. Luhrs' model fo llows well the mean displacement of the line in velocity space, but is unab le to reproduce details in the line profile and fails to give a reliable es timate of the orbital inclination. In the second method, an alternative att empt is also made to fit the variation of more global quantities, full widt h at half-maximum and radial velocity of the excess emission, with phase. T his method also gives satisfactory results in a qualitative way, but shows numerical degeneracy with orbital inclination. Colliding wind effects on th e very strong C IV 5808-Angstrom Wolf-Rayet emission line, present in all s ix binaries, are also found to behave qualitatively as expected. After allo wing for line enhancement in colliding wind binaries, it now appears that a ll Magellanic Cloud WC/WO stars occupy a very narrow range in spectral subc lass: WC4/WO3.