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Wind Collision and Accretion Simulations of the Massive Binary System HD 166734

We run hydrodynamic simulations which follow the colliding winds structure of the massive binary system HD 166734 along its binary orbit, and show that close to periastron passage the secondary wind is suppressed and the secondary accretes mass from the primary wind. The system consists two blue supergiants with masses of $M_1 \approx 39.5 ~\rm{M_\odot}$ and $M_2 \approx 30.5 ~\rm{M_\odot}$, on a $P \simeq 34.538 ~\rm{days}$ orbit with eccentricity of $e \approx 0.618$. This close O-O binary with high eccentricity is observed through its orbit in the X-rays, where it shows an unusual long minimum close to periastron passage. We use advanced simulations with wind acceleration and prescription treatment of accretion and simulate the entire orbit at high resolution that captures the instabilities in the winds. We 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 onto the secondary begins. The accretion phase lasts for $\simeq 12 ~\rm{days}$, and the amount of accreted mass per cycle we obtain is $M_{\rm{acc}} \simeq 1.3 \cdot 10^{-8} ~\rm{M_\odot}$. The accretion phase can account for the observed decline in X-ray emission from the system.