Matter supply mechanisms in X-ray binaries

The six best known X-ray binaries are investigated according to the two different assumptions on the mechanism of matter supply. From the model of a semi-detached system with a point-like component, rather good estimates for the masses of the stars and the radius of the optical component can be deduced. The stellar wind model appears to be generally insufficient for driving the X-luminosity. Therefore, according to the mass-ratios, the stars may be at the beginning of mass-exchange. Only 3U 1700-37 shows inconsistent observational data.In the frame of the Roche model, the values of the contact phase angles, in the case of one star filling its lobe and a point-like companion, are given in tabular form in the Appendix, as a function of the mass-ratio and the orbital inclination angle. The limiting minimum inclination angle to have an eclipse is also given.This work has been partly supported by a contract of the Consiglio Nazionale delle Ricerche (CNR).