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M. Gliozzi (GMU, Dept of Physics and Astronomy), I.E. Papadakis (University of Crete, Physics Department), R.M. Sambruna (GMU, Dept of Physics and Astronomy), M. Eracleous (The Pennsylvania State University, Dept of Physics and Astronomy)
We use data from a two-year intensive RXTE monitoring campaign of the broad-line radio galaxy 3C 390.3 to investigate its stationarity. In order to exploit the potential information contained in a time series more efficiently, we use a multi-technique approach. Specifically, the temporal properties are studied first with traditional linear techniques in the Fourier domain, by estimating the power spectral density, and in the time domain with a structure function analysis. Additionally we utilize techniques borrowed from the non-linear dynamics, and investigate directly the probability density function associated with the physical process underlying the signal. In this way, we demonstrate the presence at high significance level of non-stationarity, which is undetectable on the basis of the power spectral density analysis. This result indicates, for the first time, that the variability properties of the AGN light curves may also vary with time, in the same way as they do in GBHs, strengthening the analogy between the X-ray variability properties of AGN and GBHs. Financial support from NASA LTSA grants NAG5-10708 (MG, RMS), and NAG5-10817 (ME) is gratefully acknowledged.
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Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.