¹ Ústav teoretické fyziky a astrofyziky PrF MU, Kotlárská 2, CZ-611 37 Brno, Czech Republic
² Astronomický ústav, Akademie ved Ceské republiky, CZ-251 65 Ondrejov, Czech Republic

We show that the so-called Gayley-Owocki (Doppler, GO) heating is important for the temperature structure of the wind of main sequence stars cooler than the spectral type O6. The formula for GO heating is derived directly from the Boltzmann equation as a direct consequence of the dependence of the driving force on the velocity gradient. Since GO heating deposits heat directly to the absorbing ions, we also investigated the possibility that individual components of the radiatively driven stellar wind have different temperatures. This effect is negligible in the wind of O stars, whereas a significant temperature difference takes place in the winds of main sequence B stars for stars cooler than B2. Typical temperature difference between absorbing ions and other flow components for such stars is of the order 10³ K. However, in the case when passive component falls back onto the star the absorbing component reaches temperatures of order 10⁶ K, which allows for emission of X-rays. Moreover, we compare our computed terminal velocities with the observed ones. We found quite good agreement between predicted and observed terminal velocities. The systematic difference coming from the using of the so called ``cooking formula'' has been removed.

2001, A&A, 377, 175
Preprints from krticka@physics.muni.cz