X-ray and radio variability in the low luminosity Active Galactic
  Nucleus NGC 7213
  We present the results of a ~ 3 year campaign to monitor the low luminosity
active galactic nucleus (LLAGN) NGC 7213 in the radio (4.8 and 8.4 GHz) and
X-ray bands (2-10 keV). With a reported X-ray Eddington ratio of 7 x 10^-4
L_Edd, NGC 7213 can be considered to be comparable to a hard state black hole
X-ray binary. We show that a weak correlation exists between the X-ray and
radio light curves. We use the cross-correlation function to calculate a global
time lag between events in the X-ray and radio bands to be 24 +/- 12 days lag
(8.4 GHz radio lagging X-ray), and 40 +/- 13 days lag (4.8 GHz radio lagging
X-ray). The radio-radio light curves are extremely well correlated with a lag
of 20.5 +/- 12.9 days (4.8 GHz lagging 8.4 GHz). We explore the previously
established scaling relationship between core radio and X-ray luminosities and
black hole mass L_{R} \propto M^{0.6-0.8} L_{X}^{0.6}, known as the
`fundamental plane of black hole activity', and show that NGC 7213 lies very
close to the best-fit `global' correlation for the plane as one of the most
luminous LLAGN. With a large number of quasi-simultaneous radio and X-ray
observations, we explore for the first time the variations of a single AGN with
respect to the fundamental plane. Although the average radio and X-ray
luminosities for NGC 7213 are in good agreement with the plane, we show that
there is intrinsic scatter with respect to the plane for the individual data
points.
