Spectral Variability of IRAS 18325-5926 and Constraints on the Geometry of the Scattering Medium

We analyze Suzaku and XMM-Newton data of the highly variable Seyfert 2, IRAS 18325-5926. The spectra of the source are well modeled as a primary component described as an absorbed power law and a secondary power-law component which is consistent with being scattered emission from an on-axis extended highly ionized medium. We show that while the primary component varies on a wide range of timescales from 10⁴-10⁸ s, the scattered emission is variable only on timescales longer than 10⁵ s. This implies that the extent of the scattering medium is greater than 10¹⁶ cm. The ratio of the scattered to primary flux (~0.03) implies a column density for the scattering medium to be ~10²³ cm^-2. We argue that for such a medium to be highly ionized it must be located less than 10¹⁷ cm from the X-ray source. Thus, we localize the position and extent of scattering region to be ~a few × 10¹⁶ cm, with an average particle density of ~10⁶ cm^-3. We consider the physical interpretation of these results, and as an aside we confirm the presence of a broad iron line emission in both the XMM-Newton and Suzaku observations.