# OGLE-2016-BLG-0156: Microlensing Event With Pronounced Microlens-Parallax Effects Yielding Precise Lens Mass Measurement

## TL;DR

This paper analyzes a gravitational microlensing event with pronounced parallax effects, enabling precise measurement of the lens's physical parameters, revealing a binary M-dwarf system at 1.35 kpc, with implications for future observations.

## Contribution

The study demonstrates how multiple-peak microlensing light curves can tightly constrain microlens-parallax effects for accurate lens characterization.

## Key findings

- Binary M-dwarf lens with masses 0.18 and 0.16 solar masses
- Lens located at 1.35 kpc distance
- High relative lens-source proper motion of 6.94 mas/yr

## Abstract

We analyze the gravitational binary-lensing event OGLE-2016-BLG-0156, for which the lensing light curve displays pronounced deviations induced by microlens-parallax effects. The light curve exhibits 3 distinctive widely-separated peaks and we find that the multiple-peak feature provides a very tight constraint on the microlens-parallax effect, enabling us to precisely measure the microlens parallax $\pi_{\rm E}$. All the peaks are densely and continuously covered from high-cadence survey observations using globally located telescopes and the analysis of the peaks leads to the precise measurement of the angular Einstein radius $\theta_{\rm E}$. From the combination of the measured $\pi_{\rm E}$ and $\theta_{\rm E}$, we determine the physical parameters of the lens. It is found that the lens is a binary composed of two M dwarfs with masses $M_1=0.18\pm 0.01\ M_\odot$ and $M_2=0.16\pm 0.01\ M_\odot$ located at a distance $D_{\rm L}= 1.35\pm 0.09\ {\rm kpc}$. According to the estimated lens mass and distance, the flux from the lens comprises an important fraction, $\sim 25\%$, of the blended flux. The bright nature of the lens combined with the high relative lens-source motion, $\mu=6.94\pm 0.50\ {\rm mas}\ {\rm yr}^{-1}$, suggests that the lens can be directly observed from future high-resolution follow-up observations.