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 }<SUB>{{E</SUB>}}. Furthermore, the three resolved caustics allow us to measure the angular Einstein radius {θ }<SUB>{{E</SUB>}}. From the combination of {π }<SUB>{{E</SUB>}} and {θ }<SUB>{{E</SUB>}}, the physical lens parameters are uniquely determined. It is found that the lens is a binary composed of two M dwarfs with masses {M}<SUB>1</SUB>=0.52+/- 0.04 {M}<SUB>⊙ </SUB> and {M}<SUB>2</SUB>=0.42+/- 0.03 {M}<SUB>⊙ </SUB> separated in projection by {a}<SUB>\perp </SUB>=6.4+/- 0.5 {au}. The lens is located in the disk with a distance of {D}<SUB>{{L</SUB>}}=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.