Multicomponent radiatively driven stellar winds - I. Nonisothermal three-component wind of hot B stars

We computed models of a three-component nonisothermal radiatively driven st ellar wind for different spectral types of hot B stars. We showed that fric tion heats mainly tile outer parts of the wind and the modified temperature stratification leads to a decrease of the outflow velocity. Contrary to th e isothermal case; even the possibility of decoupling of radiatively absorb ing ions and (major) nonabsorbing component is excluded for a realistic for m of the driving force. Regardless of the actual form of the driving force, we derived general conditions under which decoupling of a stellar wind may occur. We demonstrated that the possibility of decoupling is closely relat ed to the functional dependence of the driving force and to the ratio of th e densities of individual components. We discuss several consequences of a multifluid phenomenon in hot star winds, particularly metallicity effects a nd the implications of possible helium decoupling on chemically peculiar st ars. We propose an explanation of the low terminal velocity of tau Sco base d on frictional heating.