X-ray Constraint on Location of AGN Torus in Circinus Galaxy
  The location of the obscuring "torus" in an active galactic nucleus (AGN) is
still an unresolved issue. The line widths of X-ray fluorescence lines
originated from the torus, particularly Fe K$\alpha$, carry key information on
the radii of line emitting regions. Utilizing XCLUMPY (Tanimoto et al. 2019),
an X-ray clumpy torus model, we develop a realistic model of emission line
profiles from an AGN torus where we take into account line broadening due to
the Keplerian motion around the black hole. Then, we apply the updated model to
the best available broadband spectra (3-100 keV) of the Circinus galaxy
observed with Suzaku, XMM-Newton, Nuclear Spectroscopic Telescope Array
(NuSTAR), and Chandra, including 0.62 Ms Chandra/HETG data. We confirm that the
torus is Compton-thick (hydrogen column-density along the equatorial plane is
$N_\mathrm{H}^\mathrm{Equ}=2.16^{+0.24}_{-0.16}\times 10^{25}\
\mathrm{cm}^{-2}$), geometrically thin (torus angular width
$\sigma=10.3^{+0.7}_{-0.3}\ \mathrm{degrees}$), viewed edge-on (inclination
$i=78.3^{+0.4}_{-0.9}\ \mathrm{degrees}$), and has super-solar abundance
($1.52^{+0.04}_{-0.06}$ times solar). Simultaneously analyzing the Chandra/HETG
first, second, and third order spectra with consideration of the spatial extent
of the Fe K$\alpha$ line emitting region, we constrain the inner radius of the
torus to be $1.9^{+3.1}_{-0.8}\times 10^5$ times the gravitational radius, or
$1.6^{+1.5}_{-0.9}\times 10^{-2}\ \mathrm{pc}$ for a black hole mass of
$(1.7\pm 0.3)\times 10^6\ M_{\odot}$. This is about 3 times smaller than that
estimated from the dust sublimation radius, suggesting that the inner side of
the dusty region of the torus is composed of dust-free gas.
