X-ray variability of 104 active galactic nuclei. XMM-Newton
  power-spectrum density profiles
  AGN, powered by accretion onto SMBHs, are thought to be scaled up versions of
Galactic black hole X-ray binaries (BH-XRBs). In the past few years evidence of
such correspondence include similarities in the broadband shape of the X-ray
variability power spectra, with characteristic bend times-scales scaling with
mass. We have performed a uniform analysis of the power spectrum densities
(PSDs) of 104 nearby (z<0.4) AGN using 209 XMM-Newton/pn observations. The PSDs
have been estimated in three energy bands: 0.2-10, 0.2-2, and 2-10 keV. The
sample comprises 61 Type-1 AGN, 21 Type-2 AGN, 15 NLSy1, and 7 BLLACS. We have
fitted each PSD to two models: (1) a single power-law model and (2) a bending
power-law model. Among the entire sample, 72% show significant variability in
at least one of the three bands tested. A high percentage of low-luminosity AGN
do not show any significant variability. The PSD of the majority of the
variable AGN was well described by a simple power-law with a mean index of 2.
In 15 sources we found that the bending power law model was preferred with a
mean slope of 3 and a mean bend frequency of 2.E-04 Hz. Only KUG1031+398
(REJ1034+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. Both
quantitative (i.e. scaling with BH mass) and qualitative (overall PSD shapes)
found in this sample of AGN are in agreement with the expectations for the
SMBHs and BH-XRBs being the same phenomenon scaled-up with the size of the BH.
The steep PSD slopes above the high frequency bend bear a closer resemblance to
those of the `soft/thermal dominated' BH-XRB states than other states.
