2020MNRAS.492.5261K

I have run hydrodynamic simulations that follow the colliding wind structure of the massive binary system HD 166734 along its binary orbit. I show that close to periastron passage the secondary wind is suppressed and the secondary accretes mass from the primary wind. The system consists of two blue supergiants with masses of M_1 ≃ 39.5 ∼M_{☉} and M_2 ≃ 30.5 ∼M_{☉}, on an orbit of P ≃ 34.538 d with an eccentricity of e ≃ 0.618. This close O-O binary with high eccentricity is observed through its orbit in X-rays, where it shows an unusually long minimum close to periastron passage. I use advanced simulations with wind acceleration and a prescription treatment of accretion and I simulate the entire orbit at high resolution, which captures the instabilities in the winds. I find that the colliding wind structure is unstable even at apastron. As the stars approach periastron passage, the secondary wind is quenched by the primary wind and the accretion on to the secondary begins. The accretion phase lasts for ≃12 d, and the amount of accreted mass obtained per cycle is M_{acc} ≃ 1.3 x 10^{-8} M_{☉ }. The accretion phase can account for the observed decline in X-ray emission from the system.