We present the analysis of the caustic-crossing binary microlensing event OGLE-2017-BLG-0039 .
Thanks to the very long duration of the event , with an event time scale t _ { E } \sim 130 days , the microlens parallax is precisely measured despite its small value of \pi _ { E } \sim 0.06 .
The analysis of the well-resolved caustic crossings during both the source star ’ s entrance and exit of the caustic yields the angular Einstein radius \theta _ { E } \sim 0.6 Â mas .
The measured \pi _ { E } and \theta _ { E } indicate that the lens is a binary composed of two stars with masses \sim 1.0 ~ { } M _ { \odot } and \sim 0.15 ~ { } M _ { \odot } , and it is located at a distance of \sim 6 kpc .
From the color and brightness of the lens estimated from the determined lens mass and distance , it is expected that \sim 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 the nature of the lens .