The O-type eclipsing binary SZ Cam revisited

We analyse new spectra of the multiple system SZ Cam because previous studies found different values of the primary radial velocity amplitude. The older solutions of light curves also have different ratios of secondary to primary luminosity as inferred from the observed equivalent widths of spectral lines. We therefore reanalyse the light curves of the eclipsing pair. Only the light curve derived by Wesselink has a solution that agrees with the observed equivalent width ratio. The resulting parameters of the binary are discussed. Masses of $M_1=16.6$ and $M_2=11.9$ M$_{\odot}$, and radii $R_1=9.4$ and $R_2=5.4$ R$_{\odot}$ are derived. We point out that radial velocities measured with the CCF method can be misleading when the method is applied to multiple systems with complex line blends. New radial velocities are also obtained for the visual component ADS 2984 A (HD 25639).