We calculated the median parallaxes for 47 OB associations including at least 10 stars with known Gaia DR2 parallaxes. A comparison between trigonometric and photometric parallaxes of OB associations reveals a zero-point offset of delta_pi=-0.11 +\- 0.04 mas indicating that Gaia DR2 parallaxes are, on average, underestimated and the distances derived from them are overestimated. The correction of delta_pi=-0.11 mas is consistent with the estimate that Arenou et al. (2018) obtained for bright stars. An analysis of parallaxes of OB associations and high-luminosity field stars confirms our previous conclusion (Dambis et al. 2001) that the distance scale for OB stars established by Blaha and Humphreys (1989) must be reduced by 10--20%. Spurious systematic motions of 10--20 km s-1 at the distances of 2--3 kpc from the Sun are found to arise from the use of the uncorrected Gaia DR2 parallaxes.

中文翻译：

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OB 协会和 Gaia DR2 场中高亮度恒星的距离标度。虚假的系统运动

我们计算了 47 个 OB 协会的中值视差，其中包括至少 10 颗具有已知 Gaia DR2 视差的恒星。OB 关联的三角和光度视差之间的比较揭示了 delta_pi=-0.11 +\- 0.04 mas 的零点偏移，表明 Gaia DR2 视差平均被低估，并且从它们导出的距离被高估。delta_pi=-0.11 mas 的修正与 Arenou 等人的估计一致。(2018) 获得明亮的星星。对 OB 协会和高亮度场星的视差分析证实了我们之前的结论 (Dambis et al. 2001)，即 Blaha 和 Humphreys (1989) 建立的 OB 星的距离尺度必须减少 10--20%。