<i>ASCA</i> Observations of Seyfert 1 Galaxies. III. The Evidence for Absorption and Emission Due to Photoionized Gas

Abstract

We present the results from a detailed analysis of the 0.610 keV spectra of 23 ASCA observations of 18 objects. We nd that in most cases the underlying continuum can be well represented by a power law with a photon index ! D 2. However, we nd strong evidence for photoionized gas in the line of sight to 13/18 objects. We present detailed modeling of this gas based upon the ION photoionization code. Other studies have been made of the "" warm absorber phenomenon, but this paper contains the rst consideration of the importance of the covering fraction of the ionized gas and a direct comparison between models of attenuation by ionized versus neutral material.