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Paper: Simulations of aperiodic and periodic variability on X ray sources
Volume: 61, Astronomical Data Analysis Software and Systems III
Page: 353
Authors: Burderi, Luciano
Abstract: There is a great deal of evidences that X ray emission from X Ray Binaries and Active Galactic Nuclei is often associated with aperiodic variations in the intensity of the emitted radiation (sometimes referred as ``flickering'') with a characteristic Power Spectrum broad band feature that roughly increase with decreasing frequency (red noise). To investigate in detail this (still unclear under many aspects) phenomenon we have developed a simulation program of time behavior of a flickering X ray source. Taking into account some physical models of the variability (basically a stochastic shot noise process), this program generates a time series of sampled data suitable to analysis through the Fast Fourier Transform techniques. Also the effects of a periodic modulation (as observed in the High Mass X Ray Binaries) can be simulated. Using slightly different models, corresponding to different physical conditions on the source ( e.g. varying the intensities and the timescales of the shots according to some particular statistical distributions), we have been able to generate power spectra of different shapes. A semiquantitative interpretation of the results is performed on the basis of general theorems of the Fourier Series theory. Further some physical considerations for each of the models considered are outlined and a comparison with observed spectra of galactic X ray binary is done.
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