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Paper: Clumpy Accretion Flows in Active Galactic Nuclei
Volume: 427, Accretion and Ejection in AGN: a Global View
Page: 112
Authors: Ishibashi, W.; Courvoisier, T. J.
Abstract: We discuss the fueling of the central black hole in active galactic nuclei in the framework of a clumpy accretion flow. Shocks between elements (clumps) forming the accretion flow are at the origin of the observed radiation. We expect a cascade of shocks, with optically thick shocks giving rise to optical/UV emission and optically thin shocks accounting for the X-ray emission. We obtain X-ray to UV luminosity ratios (LX/LUV) always smaller than unity and lower values in massive objects compared to less massive sources, consistent with the observed αOX–lUV anticorrelation. We derive a characteristic X-ray variability time scale within our model and compare it with the observed X-ray power spectral density break time scale. The predicted dependence of the variability time scale on black hole mass and accretion rate is in agreement with the observational relation obtained by McHardy et al. (2006).
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