Unveiling the physics of low luminosity AGN through X-ray variability:
  LINER versus Seyfert 2
  X-ray variability is very common in active galactic nuclei (AGN), but these
variations may not occur similarly in different families of AGN. We aim to
disentangle the structure of low ionization nuclear emission line regions
(LINERs) compared to Seyfert 2s by the study of their spectral properties and
X-ray variations. We assembled the X-ray spectral parameters and variability
patterns, which were obtained from simultaneous spectral fittings. Major
differences are observed in the X-ray luminosities, and the Eddington ratios,
which are higher in Seyfert 2s. Short-term X-ray variations were not detected,
while long-term changes are common in LINERs and Seyfert 2s. Compton-thick
sources generally do not show variations, most probably because the AGN is not
accesible in the 0.5--10 keV energy band. The changes are mostly related with
variations in the nuclear continuum, but other patterns of variability show
that variations in the absorbers and at soft energies can be present in a few
cases. We conclude that the X-ray variations may occur similarly in LINERs and
Seyfert 2s, i.e., they are related to the nuclear continuum, although they
might have different accretion mechanisms. Variations at UV frequencies are
detected in LINER nuclei but not in Seyfert 2s. This is suggestive of at least
some LINERs having an unobstructed view of the inner disc where the UV emission
might take place, being UV variations common in them. This result might be
compatible with the disappeareance of the torus and/or the broad line region in
at least some LINERs.
