Parameters of the X-ray binary system Scorpius X-1

We modelled optical light curves of Sco X-1 obtained by the Kepler Space Telescope during the K2 mission. Modelling was performed for the case of strong heating of the optical star and accretion disc by X-rays. In the model considered, the optical star fully filled its Roche lobe. We investigated the inverse problem in wide ranges of values of model parameters and estimated the following parameters of Sco X-1: the mass ratio of components q = M-x/M-v = 3.6 (3.5-3.8), where M-x and M-v are the masses of the neutron and optical stars correspondingly; the orbital inclination was i = 30 degrees (25-34 degrees). In the brackets the uncertainties of parameters q and i are shown; these originated due to uncertainties of characteristics of the physical model of Sco X-1. The temperature of the non-heated optical star was T-2 = 2500-3050 K, its radius was R-2 = 1.25R(circle dot) = 8.7 x 10(10) cm, and its bolometric luminosity was L-bol = (2.1-4.6) x 10(32) erg s(-1). The mass of the star was Mv similar or equal to 0.4M circle dot. The contribution of the X-ray-heated accretion disc dominated in the total optical emission of Sco X-1. The transition between low and high states occurred due to the increase of X-ray luminosity by a factor of 2-3.

Automated summary

The study modeled optical light curves of Sco X-1 and estimated parameters such as mass ratio, orbital inclination, temperature, radius, and luminosity. The X-ray-heated accretion disc was found to dominate the total optical emission of Sco X-1, with a transition between low and high states occurring due to an increase in X-ray luminosity by a factor of 2-3.