THE INFLUENCE OF PHOTOIONIZATION ON SHOCK-WAVE EMISSION IN FE-XXV ANDFE-XXVI ION RESONANCE TRANSITIONS DURING COLLISIONS OF RAPID CIRCUMSTELLAR FLOWS

The emission in the resonance lines of hydrogen- and helium-like iron ions behind a shock front is calculated assuming total radiative cooli ng behind the front. The calculations are performed for velocities of the unperturbed gas relative to the front 4000 km/s < u(o) < 15 000 km /s. The density of the unperturbed gas is taken to be that typical for circumstellar flows in close binary systems. The calculations take in to account the ionization of the material flowing into the front by ha rd radiation from the hot gas that has passed through the front. The r ecombination radiation of the inflowing material grows as the gas velo city increases, and exceeds the line emission of the gas behind the fr ont when u(o) > 6000 km/s. Relevance of the results for the close bina ry system SS 433 is discussed.