Peculiar rapid X-ray variability in active galactic nuclei

Black hole mass and accretion rate are two key parameters that define active galactic nuclei (AGN) and some characteristics are pronounced when observed  in X-ray. For example, rapid X-ray variability tends to be observed in systems with smaller black holes. The shape of the wide-band spectral energy distribution (SED) appears to be controlled by an accretion rate: the fraction of energy emitted in X-ray relative to the total energy output varies according to the accretion rate. These are well known facts but there are some exceptional objects. IRAS 18325-5926 is highly variable, X-ray bright AGN and one of these exceptions. Recent black hole mass estimates of this AGN from various techniques all indicate a relatively large black hole mass and a low accretion rate, which match the hard (X-ray strong) SED. However, the observed X-ray light curves show far more rapid variability than expected for the given black hole mass. This proposed project aims to quantify how unusual the X-ray variability of IRAS 18325-5926 is, compared to the general trend and to identify the characteristic size where the X-ray emission and associated spectral features are generated.