Warm absorbers in active galactic nuclei

摘要: Recent {\it ASCA} observations confirm the presence of X-ray absorption due to partially ionized gas in many Seyfert 1 galaxies; so-called warm absorber. Constraints on location material are presented with conclusion that this lies at radii coincident with, or just outside, broad-line region. The stability isobaric perturbations under assumptions thermal and photoionization equilibrium is also studied. It shown there a remarkably small range ionization parameter, $\xi$, for which absorber state stable. robustness result changes shape primary continuum, assumed density optical depth investigated. Given constraints properties material, several models environments nuclei discussed. These attempt explain significant amounts material. In particular, various region simple two-phase model proves be unsatisfactory. A turbulent, hot intercloud medium mechanically heated. Turbulent mixing layers could then give rise features. Finally, discussed steady state, radiatively driven outflow.