We successfully measured the trigonometric parallax of Sagittarius A* (Sgr A*) to be 117 ± 17 micro-arcseconds ($\, \mu \mbox{as}$) using the VLBI Exploration of Radio Astrometry (VERA) with the newly developed broad-band signal-processing system named “OCTAVE-DAS.” The measured parallax corresponds to a Galactocentric distance at the Sun of $R_0 = 8.5^{+1.5}_{-1.1}\:$kpc. By combining the astrometric results with VERA and the Very Long Baseline Array (VLBA) over a monitoring period of 25 yr, the proper motion of Sgr A* is obtained to be (μα, μδ) = (−3.133 ± 0.003, −5.575 ± 0.005) mas yr−1 in equatorial coordinates, corresponding to (μl, μb) = (−6.391 ± 0.005, −0.230 ± 0.004) mas yr−1 in Galactic coordinates. This gives an angular orbital velocity of the Sun of Ω⊙ = 30.30 ± 0.02 km s−1 kpc−1. We find upper limits to the core wander, Δθ < 0.20 mas (1.6 au), peculiar motion, Δμ < 0.10 mas yr−1 (3.7 km s−1), and acceleration, a < 2.6 $\, \mu \mbox{as} \:$yr−2 (0.10 km s−1 yr−1) for Sgr A*. Thus, we obtained upper mass limits of $\approx 3 \times 10^{4}\, M_{\odot }$ and $\approx 3 \times 10^{3}\, M_{\odot }$ for the supposed intermediate-mass black holes at 0.1 and 0.01 pc from the Galactic center, respectively.

中文翻译：

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VERA 使用新型宽带后端系统 OCTAVE-DAS 测量人马座 A* 的三角视差和自行

我们使用VLBI射电天体测量探索（VERA）和新开发的射电天体测量技术（VERA）成功测量了人马座A*（Sgr A*）的三角视差为117 ± 17微角秒（$\, \mu \mbox{as}$）名为“OCTAVE-DAS”的宽带信号处理系统。测量的视差对应于太阳的银心距离 $R_0 = 8.5^{+1.5}_{-1.1}\:$kpc。结合VERA和甚长基线阵列（VLBA）25年监测周期的天体测量结果，得到人马座A*的自行运动为（μα，μδ）=（−3.133±0.003，−5.575±赤道坐标中的 0.005) mas yr−1，对应于银河坐标中的 (μl, μb) = (−6.391 ± 0.005, −0.230 ± 0.004) mas yr−1。由此得出太阳的轨道角速度为 Ω⊙ = 30.30 ± 0.02 km s−1 kpc−1。我们发现磁芯漂移的上限，Δθ < 0.20 mas (1.6 au)，奇特运动，Δμ < 0.10 mas yr−1 (3.7 km s−1)，加速度 a < 2.6 $\, \mu \mbox{as} \:$yr−2 (0.10 km s−1 yr−1) 对于 Sgr A*。因此，我们获得了假设的质量上限 $\approx 3 \times 10^{4}\, M_{\odot }$ 和 $\approx 3 \times 10^{3}\, M_{\odot }$中等质量黑洞分别位于距银河中心 0.1 和 0.01 pc 处。