NLTE models of line-driven stellar winds - III. Influence of X-ray radiation on wind structure of O stars

We Study the influence of X-rays oil the wind structure of selected 0 stars. For this purpose we use Our non-local thermodynamic equilibrium (NLTE) wind code with inclusion of additional artificial source of X-rays, assumed to originate in the wind shocks. We show that the influence of shock X-ray emission oil wind mass-loss rate is relatively small. Wind terminal velocity may be slightly influenced by the presence of strong X-ray sources, especially for stars cooler than T(eff) less than or similar to 35 000 K. We discuss the origin of the L(X)/L similar to 10(-7) relation. For stars with thick wind this relation call be explained assuming that the cooling time depends oil wind density. Stars with optically thin winds exhibiting the 'weak wind problem' display enhanced X-ray emission which may be connected with large shock cooling, length. We propose that this effect can explain the 'weak wind problem'. Inclusion of X-rays leads to a better agreement of the model ionization Structure With observations. However, we do not find any significant influence of X-rays oil P v ionization fraction implying that the presence of X-rays cannot explain the P v problem. We Study the implications of modified ionization equilibrium due to shock emission oil the line transfer in the X-ray region. We Conclude that the X-ray line profiles Of helium-like ions may be affected by the line absorption within the cool wind.