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

TL;DR

This paper analyzes a rare five-peak gravitational microlensing event to precisely determine the lens system's physical parameters, revealing a binary of two M dwarfs in the Galactic disk with high accuracy.

Contribution

The study introduces a method leveraging the quintuple-peak light curve to tightly constrain source trajectory and measure microlensing parallax and Einstein radius, enabling precise lens characterization.

Findings

Lens is a binary of two M dwarfs with ~0.5 solar masses each.

Lens located in the Galactic disk at about 3.3 kpc.

Precise measurements of lens separation and mass.

Abstract

We present the analysis of the binary-microlensing event OGLE-2014-BLG-0289. The event light curve exhibits very unusual five peaks where four peaks were produced by caustic crossings and the other peak was produced 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 $\thetae$. From the combination of $\pi_{\rm E}$ and $\thetae$, 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 $a_\perp = 6.4 \pm 0.5$ au. The lens is located in the disk with a distance of $D_{\rm L} = 3.3 \pm 0.3$~kpc. It turns out that the reason for the absence of a lensing signal in the {\it Spitzer} data is that the time of observation corresponds to the flat region of the light curve.