Dust Coagulation in Oxygen-rich Circumstellar Outflows

We show that the inefficient growth of SiO molecules on (SiO) _x dust grains prolongs the period of maximum dust nucleation in circumstellar outflows resulting in a several orders-of-magnitude increase in the dust density near the star. This increase in dust density powers dust coagulation and results in the formation of large fractal aggregates that should be extremely efficient per unit mass in coupling to both the stellar radiation field and to the ambient gas.