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

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 $\ddot{I}{€}_{\mathrm{E}}$. 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 $\hat{I}{¸}_{\mathrm{E}}$. From the combination of the measured $\ddot{I}{€}_{\mathrm{E}}$ and $\hat{I}{¸}_{\mathrm{E}}$, we determine the physical parameters of the lens. It is found that the lens is a binary composed of two M dwarfs with masses $M_1=0.18\pm 0.01M_{\odot }$ and $M_2=0.16\pm 0.01M_{\odot }$ located at a distance $D_{\mathrm{L}}=1.35\pm 0.09\mathrm{kpc}$. 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, $\hat{I}¼=6.94\pm 0.50\mathrm{mas}{\mathrm{yr}}^{-1}$, suggests that the lens can be directly observed from future high-resolution follow-up observations.

9 pages, 9 figures