Some effects of strong gravity on AGN X-ray light curves

Patricia Arevalo (MPE)

The X-ray emission of AGN probably originates very close to the central black hole. The presence of the strong gravitational field and the relativistic velocities reached by the accretion disc in this region introduce distortions in the observed flux. The observed flux distribution will be affected mainly by Doppler boosting, depending on the motion of the source, and focusing towards the disc plane, depending on it´s radial position. The intrinsic variability will be modulated by these two effects but the magnitude of the distortions depends strongly on the nature or the variability mechanisms. Intrinsic variability produced by Lyubarskii´s model reproduces many of the observed characteristics of AGN X-ray light curves: power-law PSD, log-normal distribution of fluxes and rms-flux linear relation These characteristics can be preserved in the presence of the black hole even if the source is co-rotating with the accretion disc very close to the centre. As in this model the variability and luminosity are not dominated by discrete hot spots, relativistic effects do not introduce strong variability on Keplerian time-scales and the final observable PSDs result to be consistent with AGN data.

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