Dependence of the absorption-line profiles and radial-velocity curve of the optical star in an X-ray binary on the orbital inclination and component-mass ratio

Theoretical absorption-line profiles and radial-velocity curves for tidally deformed optical stars in X-ray binary systems are calculated assuming LTE. The variations in the profile shapes and radial velocity curve of the optical star are analyzed as a function of the orbital inclination of the X-ray binary system. The dependence of the shape of the radial-velocity curve on the orbital inclination i increases with decreasing component-mass ratio q = m(x)/m(v). The integrated line profiles and radial-velocity curves of the optical star are calculated for the Cyg X-1 binary, which are then used to estimate the orbital inclination and mass of the relativistic object: i < 43 degrees and m(x) = 8.2-12.8 M-circle dot. These estimates are in good agreement with earlier results of fitting the radial-velocity curve of Cyg X-I using a simpler model (i < 45 degrees, m(x) = 9.0-13.2 M-circle dot. (c) 2005 Pleiades Publishing, Inc.