Orbital parameters and variability of the emission spectrum for the massive binary system 103 Tau

Abstract

Based on high-resolution spectra taken near the He I 6678 Å line for the massive binary system 103 Tau, we have detected a weak absorption component belonging to the binary’s secondary component. We have measured the radial velocities of both components, improved the previously known orbital parameters, and determined the new ones. The binary has an orbital period P_orb = 58.305^d, an orbital eccentricity e = 0.277, a radial velocity semi-amplitude of the bright component K_A = 44.8 km s⁻¹, and a component mass ratio M_A/M_B = 1.77. The absence of photometric variability and the estimates of physical parameters for the primary component suggest that the binary most likely has a considerable inclination of the orbital plane to the observer, i ≈ 50°−60°. In this case, the secondary component is probably a normal dwarf of spectral type B5–B8. Based on the spectra taken near the H_α line, we have studied the variability of the emission profile. It is shown to be formed in the Roche lobe of the secondary component, but no traces of active mass exchange in the binary have been detected.