Diagnostics on the Location and Structure of Seyfert Warm Absorbers

Abstract

At least half of all Active Galaxies show the presence of strong absorption features produced by highly ionized material. These features are blueshifted, implying outflowing winds. The location of these winds is of great importance to understanding the structure of quasars. Variability of the absorption features in response to flux variations of the central source is one of the best diagnostics to constrain the location and structure of AGN winds. Here we show that the opacity in the absorber in NGC 3783 clearly changes (at a level > 10σ) in a timescale of 31 days responding to a factor of ∼ 2 change in the ionizing continuum. There is also evidence for variability in the O VI K edge (at ∼ 3σ). The observed changes are consistent with the gas producing these absorption features being close to photoionization equilibrium. The observed change in opacity implies a density > 1 × 104 cm−3, and so locates the gas within 6 pc of the X‐ray source. The scenario in which the gas is composed of a continuous radial range of ionization structures is ruled out, as in such scenario, no opacity variations are expected. Rather, the structure of the absorber is likely composed of heavily clumped gas.