We present an analysis of the caustic-crossing binary microlensing event OGLE-2017-BLG-0039. Thanks to the very long duration of the event, with a time scale t E ∼ 130 days, the microlens parallax is measured precisely despite its low value of πE ∼ 0.06. Analysis of the well-resolved caustic crossings during the source star's entrance and exit of the caustic yields an angular Einstein radius of mas. The measured and indicate that the lens is a binary composed of two stars with masses and ∼0.15 M o, and is located at a distance of ∼6 kpc. From the color and brightness of the lens estimated from its determined mass and distance, it is expected that ∼2/3 of the I-band blended flux comes from the lens. Therefore, the event is a rare case of a bright lens event for which high-resolution follow-up observations can confirm its nature.
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