OGLE-2018-BLG-1700L: Microlensing Planet in Binary Stellar System

Abstract

We report a planet in a binary that was discovered from the analysis of the microlensing event OGLE-2018-BLG-1700. We identify the triple nature of the lens from the fact that the anomaly pattern can be decomposed into two parts produced by two binary-lens events, in which one binary pair has a mass ratio of ∼0.01 between the lens components and the other pair has a mass ratio of ∼0.3. We find two sets of degenerate solutions, in which one solution has a projected separation between the primary and its stellar companion less than the angular Einstein radius (close solution), while the other solution has a separation greater than (wide solution). From the Bayesian analysis with the constraints of the event timescale and angular Einstein radius, we find that the planet has a mass of and the stellar binary components have masses of and , respectively, and the distance to the lens is . The planet is a circumstellar planet according to the wide solution, while it is a circumbinary planet according to the close solution.