Coronal winds powered by radiative driving

Abstract

A two-component phenomenological model developed originally for zeta Puppis is revised in order to model the outflows of late-type O dwarfs that exhibit the weak-wind phenomenon. With the theory's standard parameters for a generic weak-wind star, the ambient gas is heated to coronal temperatures ~ 3 x 10^{6}K at radii > 1.4 R, with cool radiativly-driven gas being then confined to dense clumps with filling factor ~ 0.02. Radiative driving ceases at radius ~ 2.1R when the clumps are finally destroyed by heat conduction from the coronal gas. Thereafter, the outflow is a pure coronal wind, which cools and decelerates reaching infinity with terminal velocity ~ 980$ km/ s.