OGLE-2018-BLG-1011Lb,c: Microlensing Planetary System with Two Giant Planets Orbiting a Low-mass Star

We report a multiplanetary system found from the analysis of microlensing event OGLE-2018-BLG-1011, for which the light curve exhibits a double-bump anomaly around the peak. We find that the anomaly cannot be fully explained by the binary-lens or binary-source interpretations and its description requires the introduction of an additional lens component. The 3L1S (three lens components and a single source) modeling yields three sets of solutions, in which one set of solutions indicates that the lens is a planetary system in a binary, while the other two sets imply that the lens is a multiplanetary system. By investigating the fits of the individual models to the detailed light curve structure, we find that the multiple-planet solution with planet-to-host mass ratios ~9.5 × 10^(−3) and ~15 × 10^(−3) are favored over the other solutions. From the Bayesian analysis, we find that the lens is composed of two planets with masses 1.8^(+3.4)_(−1.1) M_J and 2.8^(+5.1)_(−1.7) M_J around a host with a mass 0.18^(+0.33)_(−0.10) M⊙ and located at a distance 7.1^(+1.1)_(−1.5) kpc. The estimated distance indicates that the lens is the farthest system among the known multiplanetary systems. The projected planet–host separations are ⊥,2=1.8^(+2.1)_(−1.5) au (0.8^(+0.9)_(−0.6) au) and a⊥,3=0.8^(+0.9)_(−0.6) au, where the values of a ⊥,2 inside and outside the parenthesis are the separations corresponding to the two degenerate solutions, indicating that both planets are located beyond the snow line of the host, as with the other four multiplanetary systems previously found by microlensing.