The X-ray variability history of Markarian 3
  We aim at constraining the geometry of the reprocessing matter in the nearby
prototypical Seyfert 2 Galaxy Markarian 3 by studying the time evolution of
spectral components associated to the primary AGN emission and to its
Compton-scattering. We have analyzed archival spectroscopic observations of
Markarian 3 taken over the last 12 years with the XMM-Newton, Suzaku and Swift
observatories, as well as data taken during a monitoring campaign activated by
us in 2012. The timescale of the Compton-reflection component variability
(originally discovered by ASCA in the mid-'90s) is ~64 days. This upper limit
improves by more than a factor of 15 previous estimates of the
Compton-reflection variability timescale for this source. When the light curve
of the Compton-reflection continuum in the 4-5 keV band is correlated with the
15-150 keV Swift/BAT curve a delay ~1200 days is found. The cross-correlation
results are dependent on the model used to fit the spectra, although the
detection of the Compton-reflection component variability is independent of the
range of models employed to fit the data. Reanalysis of an archival Chandra
image of Markarian 3 indicates that the Compton-reflection and the Fe K-alpha
emitting regions are extended to the North up to ~300 pc. The combination of
these findings suggests that the optically-thick reprocessor in Markarian 3 is
clumpy. There is mounting experimental evidence for the structure of the
optically-thick gas and dust in the nuclear environment of nearby heavily
obscured AGN to be extended and complex. We discuss possible modifications to
the standard unification scenarios encompassing this complexity. Markarian 3,
exhibiting X-ray absorption and reprocessing on widely different spatial
scales, is an ideal laboratory to test these models (abridged).
