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P. Uttley, I. M. McHardy (University of Southampton)
Programs to monitor active galaxies with the RXTE PCA have revealed the deep similarities between AGN and XRB variability. The power spectra of AGN appear to be identical in shape to those of XRBs, showing the same characteristic flattening, but are shifted to much lower frequencies, suggesting that the characteristic `break frequency' scales inversely with black hole mass, as we might expect. Furthermore, there is now good evidence from the power spectra that AGN occupy a variety of states analogous to the canonical states seen in XRBs.
Based on these results, we discuss the science we can do with future generations of X-ray all-sky monitor (ASMs). By improving the sensitivity of current ASMs by a factor of 10, we can measure broadband power spectra of several hundred AGN at extremely low cost. Access to the timing properties of several hundred black hole systems, covering a broad range of masses and accretion rates, will greatly assist our understanding of both AGN and XRBs. Independent measures of black hole mass from reverberation mapping or masers will enable us to determine precisely how various characteristic time-scales in the power spectrum (e.g. breaks and QPOs) scale with black hole mass and accretion rate. A large sample of black hole systems will also allow us to determine how various parameters of the system affect the prevalence of the different accretion states, while the role of a variety of accretion states in AGN unification (e.g. the nature of Narrow-Line Seyfert 1s and quasars) can be determined. Cross-correlation of the AGN X-ray lightcurves with those measured in other wavebands (e.g. by the coming generation of robotic telescopes) and the ability to target AGN in different flux states with detailed observations by e.g. Chandra, XMM and Constellation-X will enable a revolution in our understanding of AGN.
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