An exploration of dust grain growth within WCd systems using an advected scalar dust model

Dust production is one of the more curious phenomena observed in massive binary systems with interacting winds. The high temperatures, UV photon flux, and violent shocks should destroy any dust grains that condense. However, in some extreme cases, dust production yields of approximately 30 per cent of the total mass-loss rate of the stellar winds have been observed. In order to better understand this phenomenon, a parameter space exploration was performed using a series of numerical models of dust producing carbon phase Wolf–Rayet (WCd) systems. These models incorporated a passive scalar dust model simulating dust growth, destruction, and radiative cooling. We find that reasonable dust yields were produced by these simulations. Significant changes in the dust yield were caused by changing the mass-loss rates of the stars, with a greater mass-loss rate contributing to increased dust yields. Similarly, a close orbit between the stars also resulted in higher dust yields. Finally, a high-velocity wind shear, which induces Kelvin–Helmholtz (KH) instabilities and wind mixing, drastically increases the dust yields.