Distances of the TeV SNR complex CTB 37 towards the Galactic Bar
  Three supernova remnants form the CTB 37 complex: CTB 37A (G348.5+0.1,
associated with the TeV $\gamma$-ray source HESS J1714-385), CTB 37B
(G348.7+0.3, associated with HESS J1713-381 and the magnetar CXOU
J171405.7.381031), and G348.5-0.0. We use 21 cm HI absorption measurements to
constrain the kinematic distances to these SNRs, which have not previously been
determined well. We revise the kinematic distance for CTB 37A to be in the
range 6.3 to 9.5 kpc (previously $\sim$11.3 kpc) because it is beyond the near
3-kpc arm and in front of the far side of the CO cloud at -145 km s$^{-1}$
towards $l$=348.5. G348.5-0.0 has a HI column density (N$_{HI}$
$\sim6.1\times10^{21}$ cm$^{-2}$) lower than CTB 37A ($\sim7.1\time10^{21}$
cm$^{-2}$). Also, G348.5-0.0 does not have the major absorption feature at -107
km s$^{-1}$ that CTB 37A shows. This is caused by the near 3-kpc arm, so
G348.5-0.0 is at a distance of $\le$ 6.3 kpc. CTB 37B is at a distance of
$\sim$13.2 kpc (previously 5 to 9 kpc) based on: 1) it has an absorption
feature at -10$\pm$5 km s$^{-1}$ from the far 3-kpc arm, so CTB 37B is behind
it; 2) there is absorption at -30 km s$^{-1}$ but not at -26 km s$^{-1}$, which
yields the distance value; 3) the HI column density towards CTB 37B
($\sim8.3\times10^{21}$ cm$^{-2}$) is larger than CTB 37A. In summary, CTB 37A,
CTB 37B and G348.5+0.0 are all at different distances and are only by chance
nearby each other on the sky. In addition, we conclude that CTB 37 A and B are
not associated with the historical Supernova AD 393.
