Abstract

We present the observations and analysis of a high-magnification microlensing planetary event, KMT-2022-BLG-0440, for which the weak and short-lived planetary signal was covered by both the KMTNet survey and follow-up observations. The binary-lens models with a central caustic provide the best fits, with a planet/host mass ratio, q=0.75q = 0.75--1.00×1041.00 \times 10^{-4} at 1σ1\sigma. The binary-lens models with a resonant caustic and a brown-dwarf mass ratio are both excluded by Δχ2>70\Delta\chi^2 > 70. The binary-source model can fit the anomaly well but is rejected by the ``color argument'' on the second source. From Bayesian analyses, it is estimated that the host star is likely a K or M dwarf located in the Galactic disk, the planet probably has a Neptune-mass, and the projected planet-host separation is 1.90.7+0.61.9^{+0.6}_{-0.7} or 4.61.7+1.44.6^{+1.4}_{-1.7} au, subject to the close/wide degeneracy. This is the third q<104q < 10^{-4} planet from a high-magnification planetary signal (A65A \gtrsim 65). Together with another such planet, KMT-2021-BLG-0171Lb, the ongoing follow-up program for the KMTNet high-magnification events has demonstrated its ability in detecting high-magnification planetary signals for q<104q < 10^{-4} planets, which are challenging for the current microlensing surveys.Comment: MNRAS accepte

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