Evolution of the X-ray Binary System Sco X-1 within the Framework of the Induced Stellar Wind Model

Abstract

Within the framework of the induced stellar wind (ISW) model, the possible evolution of the X-ray binary system Sco X-1 after the formation of a neutron star in it is simulated and theoretically reproduced. We showed that, within the allowable limits of the ISW model parameter interval, it is possible to reproduce the system characteristics obtained earlier in the model of incomplete filling of the Roche lobe with a donor—an optical star (with a filling factor of 0.38) by modeling the optical orbital light curves of Sco X-1. The high rate of mass loss by the donor is due to its irradiation with hard radiation arising from accretion onto a neutron star. In the tracks that seem to be the most suitable for the evolution of Sco X-1, we obtained the same filling factor of the Roche lobe by the donor (0.38). According to the results of our calculations, the most probable value of the initial mass of the donor at the time of formation of a neutron star in the system does not greatly exceed its current mass $\sim {\kern 1pt} 0.4 {{M}_{ \odot }}$ and can be close to (0.5–0.7) ${{M}_{ \odot }}$. The ratio of the donor stellar wind velocity to the parabolic velocity on its surface α_ISW in our calculations turns out to be close to 0.5–0.6. The main meaning of this parameter in our model is to determine the fraction of the donor matter captured by the accretor. With such ${{\alpha }_{{{\text{ISW}}}}}$, this fraction is quite large, which is necessary for the appearance of an intense ISW. However, in a real system, there may be processes that increase this fraction even at high wind speeds. Thus, its real rate can be higher than the rate corresponding to values of ${{\alpha }_{{{\text{ISW}}}}}$ obtained by us.