We report astrometric observations of H2O masers around the red supergiant VY
Canis Majoris (VY CMa) carried out with VLBI Exploration of Radio Astrometry
(VERA). Based on astrometric monitoring for 13 months, we successfully measured
a trigonometric parallax of 0.88 +/- 0.08 mas, corresponding to a distance of
1.14 +0.11/-0.09 kpc. This is the most accurate distance to VY CMa and the
first one based on an annual parallax measurement. The luminosity of VY CMa has
been overestimated due to a previously accepted distance. With our result, we
re-estimate the luminosity of VY CMa to be (3 +/- 0.5) x 10^5 L_sun using the
bolometric flux integrated over optical and IR wavelengths. This improved
luminosity value makes location of VY CMa on the Hertzsprung-Russel (HR)
diagram much closer to the theoretically allowable zone (i.e. the left side of
the Hayashi track) than previous ones, though uncertainty in the effective
temperature of the stellar surface still does not permit us to make a final
conclusion.Comment: 7 pages, 4 figures, accepted for publication in PASJ, VERA special
issu