  We use X-ray monitoring data obtained over a broad range of time-scales to
measure the broadband power spectral density functions (PSDs) of two Seyfert
galaxies, the broad line Seyfert 1 NGC 3227 and the Seyfert 2 NGC 5506, which
has recently been identified as an obscured Narrow Line Seyfert 1 (NLS 1).
Using a Monte-Carlo fitting technique we demonstrate that both PSDs are
reminiscent of the PSD of black hole X-ray binaries (BHXRBs) in the high/soft
state, and specifically rule out a low/hard state PSD shape in NGC 3227. This
result demonstrates that, at least where variability is concerned, broad line
Seyferts with hard X-ray spectra (photon index~1.6) are not simply the
analogues of the low/hard state in BHXRBs, and the dichotomy of NLS 1 and broad
line Seyferts cannot be simply interpreted in terms of the two states. We show
that the PSD normalisation in NGC 3227 is strongly energy dependent, with
larger variability amplitudes at lower energies, unlike NGC 5506 which shows
little energy-dependence of variability. We demonstrate that this difference is
caused by spectral pivoting of the continuum in NGC 3227 at high energies,
which is probably also related to the large amplitude of variability seen in
the 2-10 keV band in this AGN. Using the new PSD data and new results in the
literature, we replot the PSD break time-scale versus mass plot for all AGN
with PSD breaks measured so far, and demonstrate that higher accretion-rate AGN
appear to have relatively shorter break time-scales for their black hole mass
than lower-accretion rate AGN.
