Trigonometric parallax and proper motion of Sagittarius A* measured by VERA using the new broad-band back-end system OCTAVE-DAS

We successfully measured the trigonometric parallax of Sagittarius A* (SgrA*) to be $117\pm17$ micro-arcseconds ($\mu$as) using the VLBI Exploration ofRadio Astrometry (VERA) with the newly developed broad-band signal-processingsystem named OCTAVE-DAS. The measured parallax corresponds to a Galactocentricdistance at the Sun of $R_0 = 8.5^{+1.5}_{-1.1}$ kpc. By combining theastrometric results with VERA and the Very Long Baseline Array (VLBA) over amonitoring period of 25 years, the proper motion of Sgr A* is obtained to be$(\mu_\alpha, \mu_\delta) = (-3.133\pm0.003, -5.575\pm0.005)$ mas yr$^{-1}$ inequatorial coordinates, corresponding to $(\mu_l, \mu_b) = (-6.391\pm0.005,-0.230\pm0.004)$ mas yr$^{-1}$ in Galactic coordinates. This gives an angularorbital velocity of the Sun of $\Omega_\odot = 30.30 \pm 0.02$ km s$^{-1}$kpc$^{-1}$. We find upper limits to the core wander, $\Delta \theta < 0.20$ mas(1.6 AU), peculiar motion, $\Delta \mu < 0.10$ mas yr$^{-1}$ (3.7 km s$^{-1}$),and acceleration, $a < 2.6$ $\mu$as yr$^{-2}$ (0.10 km s$^{-1}$ yr$^{-1}$) forSgr A*. Thus, we obtained upper mass limits of $\approx$ 3 $\times$10$^{4}$$M_{\odot}$ and $\approx$ 3 $\times$ 10$^{3}$$M_{\odot}$ for thesupposed intermediate-mass black holes at 0.1 and 0.01 pc from the Galacticcenter, respectively.