Abstract
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) similar to 130 days, the microlens parallax is measured precisely despite its low value of pi(E) similar to 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 theta(E) similar to 0.6 mas. The measured pi(E) and theta(E) indicate that the lens is a binary composed of two stars with masses similar to 1.0 M-circle dot and similar to 0.15 M-circle dot, and is located at a distance of similar to 6 kpc.
From the color and brightness of the lens estimated from its determined mass and distance, it is expected that similar to 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.