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Abstract

We present the analysis of the binary-microlensing event OGLE-2014-BLG-0289. The event light curve exhibits five very unusual peaks, four of which were produced by caustic crossings and the other by a cusp approach. It is found that the quintuple-peak features of the light curve provide tight constraints on the source trajectory, enabling us to precisely and accurately measure the microlensing parallax ${\pi }_{{\rm{E}}}$. Furthermore, the three resolved caustics allow us to measure the angular Einstein radius ${\theta }_{{\rm{E}}}$. From the combination of ${\pi }_{{\rm{E}}}$ and ${\theta }_{{\rm{E}}}$, the physical lens parameters are uniquely determined. It is found that the lens is a binary composed of two M dwarfs with masses ${M}_{1}=0.52\pm 0.04\ {M}_{\odot }$ and ${M}_{2}=0.42\pm 0.03\ {M}_{\odot }$ separated in projection by ${a}_{\perp }=6.4\pm 0.5\,\mathrm{au}$. The lens is located in the disk with a distance of ${D}_{{\rm{L}}}=3.3\pm 0.3\,\mathrm{kpc}$. The reason for the absence of a lensing signal in the Spitzer data is that the time of observation corresponds to the flat region of the light curve.