OGLE-2014-BLG-0289: Precise Characterization of a Quintuple-peak Gravitational Microlensing Event

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 π_E. Furthermore, the three resolved caustics allow us to measure the angular Einstein radius θ_E. From the combination of π_E and θ_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 ± 0.04 M_⊙ and M_2 = 0.42 ± 0.03 M_⊙ separated in projection by α_⊥ = 6.4 ± 0.5 au. The lens is located in the disk with a distance of D_L = 3.3 ± 0.3 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.