Wolf-Rayet stars mass-loss rates determined from spectroscopic measurements of the orbital evolution for close WR+OB binary systems

The most reliable method for estimating the rate of mass-loss by the Wolf–Rayet stars wind is based on the assessment of secular variations in the orbital periods for close binary systems containing such stars, most often WR+OB systems. Previously, almost only photometric observations of well-studied eclipsing close WR+OB binaries were used for these purposes. This report describes the results of the work on the search for mass-loss-induced evolutionary variations in the orbital period for close WR+OB binaries and the mass-loss rates measurements for WR stars in these systems. Orbital period variations were detected in five systems studied: V444 Cyg, CQ Cep, CX Cep, WR 127 (Hen 3-1772), and WR 141 (V2183 Cyg). In addition, phase deviations between the radial velocity curves obtained at different epochs are suspected for the A pair of the GP Cep quadruple system. For eclipsing systems, estimates of the rate of change of the orbital period from the radial velocity curves are in good agreement with the corresponding estimates obtained from the light curves. A secular shortening of the orbital period has been confirmed for the CQ Cep system, which can be explained by the high degree of closeness of this system and the associated mass transfer processes. For the WR 127 and WR 141 systems, dynamic estimates of the change of the orbital period and the rate of mass loss have been obtained for the first time. Estimates of the rate of mass-loss by Wolf-Rayet stars show a power-law dependence on the mass of the star with an exponent of about 2. The effect of the finite size of stars, which turns out to be significant for estimates of the rate of mass loss to the wind in the closest systems, is discussed.