The properties of the clumpy torus and BLR in the polar-scattered
  Seyfert 1 galaxy ESO 323-G77 through X-ray absorption variability
  We report results from multi-epoch X-ray observations of the polar-scattered
Seyfert 1 galaxy ESO 323-G77. The source exhibits remarkable spectral
variability from months to years timescales. The observed spectral variability
is entirely due to variations of the column density of a neutral absorber
towards the intrinsic nuclear continuum. The column density is generally
Compton-thin ranging from a few times 10$^{22}$ cm$^{-2}$ to a few times
10$^{23}$ cm$^{-2}$. However, one observation reveals a Compton-thick state
with column density of the order of 1.5 $\times$ 10$^{24}$ cm$^{-2}$. The
observed variability offers a rare opportunity to study the properties of the
X-ray absorber(s) in an active galaxy. We identify variable X-ray absorption
from two different components, namely (i) a clumpy torus whose individual
clumps have a density of $\leq$ 1.7 $\times$ 10$^8$ cm$^{-3}$ and an average
column density of $\sim$ 4 $\times$ 10$^{22}$ cm$^{-2}$, and (ii) the broad
line region (BLR), comprising individual clouds with density of 0.1-8 $\times$
10$^9$ cm$^{-3}$ and column density of 10$^{23}$-10$^{24}$ cm$^{-2}$. The
derived properties of the clumpy torus can also be used to estimate the torus
half-opening angle, which is of the order of 47 $^\circ$. We also confirm the
previously reported detection of two highly ionized warm absorbers with outflow
velocities of 1000-4000 km s$^{-1}$. The observed outflow velocities are
consistent with the Keplerian/escape velocity at the BLR. Hence, the warm
absorbers may be tentatively identified with the warm/hot inter-cloud medium
which ensures that the BLR clouds are in pressure equilibrium with their
surroundings. The BLR line-emitting clouds may well be the cold, dense clumps
of this outflow, whose warm/hot phase is likely more homogeneous, as suggested
by the lack of strong variability of the warm absorber(s) properties during our
monitoring.
