Outer Rotation Curve of the Galaxy with VERA II: Annual Parallax and
  Proper Motion of the Star-Forming Region IRAS21379+5106
  We conducted astrometric VLBI observations of water-vapor maser emission in
the massive star forming region IRAS 21379+5106 to measure the annual parallax
and proper motion, using VERA. The annual parallax was measured to be $0.262
\pm 0.031$ mas corresponding to a trigonometric distance of
$3.82^{+0.51}_{-0.41}$ kpc. The proper motion was $(\mu_\alpha\cos{\delta},
\mu_\delta)=(-2.74 \pm 0.08, -2.87 \pm 0.18)$ mas yr$^{-1}$. Using this result,
the Galactic rotational velocity was estimated to be $V_\theta=218\pm 19$ km
s$^{-1}$ at the Galactocentric distance $R=9.22\pm0.43$ kpc, when we adopted
the Galactic constants $R_0=8.05\pm 0.45$ kpc and $V_0=238\pm 14$ km s$^{-1}$.
With newly determined distance, {the bolometric luminosity of the central young
stellar object was re-evaluated to $(2.15\pm 0.54)\times 10^3 L_\odot$, which
corresponds to spectral type of} B2--B3. Maser features were found to be
distributed along a straight line from south-west to north-east. In addition, a
vector map of the internal motions constructed from the residual proper motions
implies that maser features trace a bipolar flow and that it cannot be
explained by simple ballistic motion.
