ASTROMETRIC OBSERVATION OF MIRA VARIABLES WITH VERA

The calibration of the period luminosity relation (PLR) for Galactic Mira variables is one of the principle aims of the VERA project. We observe $H_2O$ maser emission at 22 GHz associated with Mira variables in order to determine their distances based on annual parallaxes. We conduct multi-epoch VLBI observations over 1-2 years with a typical interval of one month using VERA in order to obtain annual parallaxes with an accuracy of better than than 10%. Recently, the annnual parallax of T Lep was determined to be $3.06{\pm}0.04$ mas corresponding to a distance of $327{\pm}4pc$ (Nakagawa et al., 2014). The circumstellar distribution and kinematics of $H_2O$ masers was also revealed. With accurate distances to the sources, calibrations of K-band absolute magnitudes ($M_K$) can be improved compared to conventional studies. By compiling Mira variables whose distances were determined with astrometric VLBI, we obtained a PLR of $M_K=3.51logP+1.37{\pm}0.07$.