Long Timescale Variability of AGN with RXTE

In this paper we review the very large contribution made by RXTE to our understanding of Active Galaxies (AGN). We discuss the relationship between AGN and Galactic Black Hole X‐ray binary systems (GBHs) and show, by comparison of their powerspectral densities (PSDs) that some AGN are the equivalent of GBHs in their ‘high’ state, rather than in their ‘low’ state as has previously been assumed. We plot the timescale at which the PSD slope steepens from −1 to −2 against the black hole mass for a sample of AGN, and for Cyg X‐1 in its high and low states. We find it is not possible to fit all AGN to the same linear scaling of break timescale with black hole mass. However broad line AGN are consistent with a linear scaling of break timescale with mass from Cyg X‐1 in its low state and NLS1 galaxies scale better with Cyg X‐1 in its high state, although there is an exception, NGC3227. We suggest that the relationship between black hole mass and break timescale is a function of another underlying parameter which ...