KMT-2018-BLG-1025Lb: microlensing super-Earth planet orbiting a low-mass star

Abstract

We aim to find missing microlensing planets hidden in the unanalyzed lensing events of previous survey data. For this purpose, we conduct a systematic inspection of high-magnification microlensing events, with peak magnifications $A_{\mathrm{peak}}\gtrsim 30$, in the data collected from high-cadence surveys in and before the 2018 season. From this investigation, we identify 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. 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 $q\sim 0.8\times 10^{-4}$ for the solution A and $q\sim 1.6\times 10^{-4}$ for the 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 $(M_{\mathrm{p}},M_{\mathrm{h}},D_{\mathrm{L}})\sim (6.1M_{\oplus },0.22M_{\odot },6.7\mathrm{kpc})$ for the solution A and $\sim (4.4M_{\oplus },0.08M_{\odot },7.5\mathrm{kpc})$ for the 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, discovered by microlensing.

10 pages, 10 figures, 5 tables

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• Systematic KMTNet Planetary Anomaly Search, Paper I: OGLE-2019-BLG-1053Lb, A Buried Terrestrial Planet
• Systematic KMTNet Planetary Anomaly Search. V. Complete Sample of 2018 Prime-Field
• Microlensing events indicate that super-Earth exoplanets are common in Jupiter-like orbits
• Systematic KMTNet Planetary Anomaly Search, Paper VII: Complete Sample of $q<10^{-4}$ Planets from the First Four-Year Survey
• Three microlensing planets with no caustic-crossing features
• KMT-2019-BLG-0797: binary-lensing event occurring on a binary stellar system
• OGLE-2019-BLG-0304: Competing Interpretations between a Planet-binary Model and a Binary-source + Binary-lens model
• MOA-2022-BLG-249Lb: Nearby microlensing super-Earth planet detected from high-cadence surveys
• Identifying low-amplitude pulsating stars through microlensing observations
• Binary-lens Microlensing Degeneracy: Impact on Planetary Sensitivity and Mass-ratio Function
• Three faint-source microlensing planets detected via resonant-caustic channel
• KMT-2018-BLG-1988Lb: microlensing super-Earth orbiting a low-mass disk dwarf
• OGLE-2019-BLG-0468Lb,c: two microlensing giant planets around a G-type star