Microlensing is able to reveal multiple body systems located several kilo-parsec away from the Earth. Since it does not require the measurement of light from the lens, microlensing is sensitive to a range of objects, from free-floating planets to stellar black holes. But, if the lens emits enough light, the microlensing model predictions can be tested with high-resolution imaging and/or radial velocity methods. Such a follow-up was done for the microlensing event OGLE-2011-BLG-0417, which was expected to be a close by (≤1 kpc), low-mass (~0.8 M ⊙) binary star with a period of P?~?1.4 year. The spectroscopic follow-up observations conducted with the Very Large Telescope did not measure any variation in the radial velocity, which is in strong contradiction with the published microlensing model. In the present work, we remodel this event and find a simpler model that is in agreement with all the available measurements, including the recent Gaia Data Release 2 parallax constraints. We also present a new way to distinguish degenerate models using the Gaia Data Release 2 proper motions. This work stresses the importance of thorough microlensing modeling, especially with the horizon of the Wide Field Infrared Survey Telescope and the Euclid microlensing space missions.
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机译：微透镜能够揭示距离地球几千帕秒的多个人体系统。由于它不需要测量来自透镜的光，因此微透镜对从自由漂浮的行星到恒星黑洞的一系列物体都非常敏感。但是，如果透镜发出足够的光，则可以使用高分辨率成像和/或径向速度方法测试微透镜模型的预测。对微透镜事件OGLE-2011-BLG-0417进行了这样的跟踪，该事件被认为是一个接近（≤1 kpc），低质量（〜0.8 M⊙）的双星，周期为P？ 〜？1.4年。用超大型望远镜进行的光谱跟进观察并未测量径向速度的任何变化，这与已发布的微透镜模型强烈矛盾。在目前的工作中，我们对事件进行了重新建模，并找到了一个与所有可用测量（包括最近的Gaia Data Release 2视差约束）相一致的简单模型。我们还提供了一种使用Gaia Data Release 2正确运动来区分退化模型的新方法。这项工作强调了彻底的微透镜建模的重要性，尤其是在宽视野红外测量望远镜和Euclid微透镜太空任务的视野下。
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