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 }<SUB>{{E</SUB>}} (close solution), while the other solution has a separation greater than {θ }<SUB>{{E</SUB>}} (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}<SUB>-2.0</SUB><SUP>+3.0</SUP> {M}<SUB>{{J</SUB>}} and the stellar binary components have masses of {0.42}<SUB>-0.19</SUB><SUP>+0.29</SUP> {M}<SUB>⊙ </SUB> and {0.12}<SUB>-0.05</SUB><SUP>+0.08</SUP> {M}<SUB>⊙ </SUB>, respectively, and the distance to the lens is {D}<SUB>{{L</SUB>}}={7.6}<SUB>-0.9</SUB><SUP>+1.2</SUP> {kpc}. The planet is a circumstellar planet according to the wide solution, while it is a circumbinary planet according to the close solution.