X-ray variability of 104 active galactic nuclei

Abstract

We have performed a uniform analysis of the power spectrum densities (PSDs) of 104 nearby (z<0.4) active galactic nuclei (AGN) using 209 XMM-Newton/pn observations, including several AGN classes. These PSDs span ≃ 3 decades in temporal frequencies, ranging from minutes to days. We have fitted each PSD to two models: (1) a single power-law model and (2) a bending power-law model. A fraction of 72% show significant variability. The PSD of the majority of the variable AGN was well described by a simple power-law with a mean index of α = 2.01±0.01. In 15 sources we found that the bending power law model was preferred with a mean slope of α = 3.08±0.04 and a mean bend frequency of ã€̂ν b〉 ≃ 2 × 10-4 Hz. Only KUG 1031+398 (RE J1034+396) shows evidence for quasi-periodic oscillations. The 'fundamental plane' relating variability timescale, black hole mass, and luminosity is demonstrated using the new X-ray timing results presented here together with a compilation of the previously detected timescales from the literature. © International Astronomical Union 2013.