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

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 θ_E (close solution), while the other solution has a separation greater than θ_E (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 4.4^(+3.0)_(−2.0) M_J and the stellar binary components have masses of 0.42^(+0.29)_(−0.19) M_⊙ and 0.12^(+0.08)_(−0.05) M_⊙, respectively, and the distance to the lens is D_L=7.6^(+1.2)_(−0.9) kpc. The planet is a circumstellar planet according to the wide solution, while it is a circumbinary planet according to the close solution.