We report phase-referencing VLBA observations of H2O masers near the star-forming region W3(OH) to measure their parallax and absolute proper motions. The measured annual parallax is 0.489 ±0.017 mas (2.04 ±0.07 kpc), where the error is dominated by a systematic atmospheric contribution. This distance is consistent with photometric distances from previous observations and with the distance determined from CH3OH maser astrometry presented in a related paper. We also find that the source driving the H2O outflow, the 'TW-object,' moves with a three-dimensional velocity of >7 km s-1 relative to the ultracompact H II region W3(OH).
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机译：我们报告了恒星形成区域W3（OH）附近H2O masers的相参考VLBA观测，以测量其视差和绝对正确的运动。测得的年视差为0.489±0.017 mas（2.04±0.07 kpc），其中误差由系统的大气贡献决定。该距离与先前观察到的光度距离以及相关论文中通过CH3OH maser天体测定法确定的距离一致。我们还发现，驱动H2O流出的源“ TW对象”相对于超紧凑型H II区域W3（OH）以大于7 km s-1的三维速度运动。
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