Power Spectral Distribution of the BL Lacertae Object S5 0716+714

Abstract

Observational data in the BVRI bands of the variable BL Lacertae Object S5 0716+714 is discussed from the point of view of its Power Spectral Distribution (PSD). Analysis of the noise properties exhibited by the source. Assessment of the validity of a turbulent model. We fitted a model of the type $P(f) = βf^{-α} + γ$ to the data for two null hypothesis and calculated the Bayesian p parameter for the fits. Different theoretical models are discussed and applied to these data and a special focus is placed on the MagnetoRotational Instability (MRI). The $P(f) = βf^{-α}$ fit provides slopes with values ranging from 0.376 to 2.237, with medium values for each band of $\barα_B = 1.756$, $\barα_V = 1.704$, $\barα_R = 1.780$ and $\barα_I = 1.272$ respectively. An interval for the calculated effective $α_{SS}$ parameter is obtained to be $[0.18,1.72]\cdot 10^{-2}$, corresponding to the order of magnitude previously inferred through both observational and numerical investigations. Structure function analysis, fractal dimension analysis and DFT analysis (all performed in other studies) plus our own analysis establish that the source is turbulent in a nontrivial way, i.e. there is "intrinsic" noise superimposed on the deterministic behavior of the source. We propose that embedding a weakly stochastic magnetic field component in the MRI (MagnetoRotational Instability) framework and taking into account stochastic reconnection of magnetic field lines might explain microvariability in AGN objects.