7 Discussion

The absolute parameters of our program stars are listed in Table 8. In the case of V337 Aql the radius of the Roche lobe-filling secondary component is considerably larger than the corresponding MS value; this is however common among early-type semi-detached systems. In the case of V649 Cas, the masses and radii of the primary and secondary components resemble main sequence values for types B 0.5 and B 4, respectively (see, e.g., Harmanec 1988). V382 Cyg is probably the earliest known contact system, so a comparison with other objects is difficult. The last case - V431 Pup - belongs to the rare early-type systems with evolved primaries. It might be compared with V380 Cyg, see the recent study by Guinan et al. (2000), and with V373 Cas (Hill & Fisher 1987), all three having somewhat longer periods and non-zero eccentricities (similarly to V373 Cas, the primary component of V431 Pup is rotating faster than synchronously). Hopefully, a good phase coverage of the radial velocity curve will allow for an application of a disentangling method in order to determine the radial velocity curves more accurately, especially the one of the secondary component. Of course, better phase and broader spectral coverage would help to derive more definite parameters also in the other cases.

Acknowledgements

We are grateful to Dr. Napiwotzki for providing us synthetic spectra, which could be compared with the observed spectrum of V382 Cyg. We are indebted to colleagues from Hvar Observatory, who measured for us the star V649 Cas (Dr. Bozic, Mr. Ruzdjak, and Mr. Sudar). We also thank the referee Dr. N. Morrell for valuable suggestions.