2021A&A...649A..90H

Aims. We aim to find missing microlensing planets hidden in the unanalyzed lensing events of previous survey data.
Methods. For this purpose, we conducted a systematic inspection of high-magnification microlensing events, with peak magnifications of A_peak≥30, in the data collected from high-cadence surveys in and before the 2018 season. From this investigation, we identified an anomaly in the lensing light curve of the event KMT-2018-BLG-1025. The analysis of the light curve indicates that the anomaly is caused by a very low mass-ratio companion to the lens.
Results. We identify three degenerate solutions, in which the ambiguity between a pair of solutions (solutions B) is caused by the previously known close-wide degeneracy, and the degeneracy between these and the other solution (solution A) is a new type that has not been reported before. The estimated mass ratio between the planet and host is q∼0.8x10^–4 for solution A and q∼1.6x10^–4 for solutions B. From the Bayesian analysis conducted with measured observables, we estimate that the masses of the planet and host and the distance to the lens are (M_p, M_h, D_L)~(6.1M_⊕, 0.22M_☉, 6.7kpc) for solution A and ~(4.4M_⊕, 0.08M_☉, 7.5kpc) for solutions B. The planet mass is in the category of a super-Earth regardless of the solutions, making the planet the eleventh super-Earth planet, with masses lying between those of Earth and the Solar System's ice giants, which were discovered by microlensing.