OGLE-2018-BLG-0567Lb and OGLE-2018-BLG-0962Lb: Two Microlensing Planets through the Planetary-caustic Channel

Albrow²,

Chung³

et al. 2021

A&A

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Aims. We present the analysis of the microlensing event KMT-2018-BLG-1743. The analysis was conducted as a part of the project, in which previous lensing events detected in and before the 2019 season by the KMTNet survey were reinvestigated with the aim of finding solutions of anomalous events with no suggested plausible models. Methods. The light curve of the event, with a peak magnification Apeak ~ 800, exhibits two anomaly features, one around the peak and the other on the falling side of the light curve. An interpretation with a binary lens and a single source (2L1S) cannot describe the anomalies. By conducting additional modeling that includes an extra lens (3L1S) or an extra source (2L2S) relative to a 2L1S interpretation, we find that 2L2S interpretations with a planetary lens system and a binary source best explain the observed light curve with Δχ2 ~ 188 and ~91 over the 2L1S and 3L1S solutions, respectively. Assuming that these Δχ2 values are adequate for distinguishing the models, the event is the fourth 2L2S event and the second 2L2S planetary event. The 2L2S interpretations are subject to a degeneracy, resulting in two solutions with s > 1.0 (wide solution) and s < 1.0 (close solution). Results. The masses of the lens components and the distance to the lens are (Mhost/M⊙,Mplanet/MJ,DL/kpc)~(0.19−0.111+0.27,0.25−0.14+0.34,6.48−1.03+0.94) and ~(0.42−0.25+0.34,1.61−0.97+1.30,6.04−1.27+0.93) according to the wide and close solutions, respectively. The source is a binary composed of an early G dwarf and a mid M dwarf. The values of the relative lens-source proper motion expected from the two degenerate solutions, μwide ~ 2.3 mas yr−1 and μclose ~ 4.1 mas yr−1, are substantially different, and thus the degeneracy can be broken by resolving the lens and source from future high-resolution imaging observations.

KMT-2018-BLG-1743: planetary microlensing event occurring on two source stars

Albrow²,

Chung³

et al. 2021

A&A

Self Cite

Three faint-source microlensing planets detected via the resonant-caustic channel

Udalski

Kim

et al. 2021

A&A

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Aims. We conducted a project of reinvestigating the 2017-2019 microlensing data collected by high-cadence surveys with the aim of finding planets that were missed due to the deviations of planetary signals from the typical form of short-term anomalies. Methods. The project led us to find three planets, KMT-2017-BLG-2509Lb, OGLE-2017-BLG-1099Lb, and OGLE-2019 The lensing light curves of the events have a common characteristic: the planetary signals were produced by the crossings of faint source stars over the resonant caustics formed by giant planets located near the Einstein rings of host stars.Results. For all planetary events, the lensing solutions are uniquely determined without any degeneracy. It is estimated that the host masses are in the range of 0.45 M/M 0.59, which corresponds to early M to late K dwarfs, and thus the host stars are less massive than the Sun. On the other hand, the planets, with masses in the range of 2.1 M/M J 6.2, are heavier than the heaviest planet of the Solar System, that is, Jupiter. The planets in all systems lie beyond the snow lines of the hosts, and thus the discovered planetary systems, together with many other microlensing planetary systems, support the idea that massive gas-giant planets are commonplace around low-mass stars. We discuss the role of late-time high-resolution imaging in clarifying resonant-image lenses with very faint sources.

KMT-2018-BLG-1988Lb: Microlensing super-Earth orbiting a low-mass disk dwarf

Gould

Albrow

et al. 2022

A&A

Self Cite

Aims. We reexamine high-magnification microlensing events in the previous data collected by the KMTNet survey with the aim of finding planetary signals that were not noticed before. In this work, we report the planetary system KMT-2018-BLG-1988L, which was found from this investigation. Methods. The planetary signal appears as a deviation with ≲0.2 mag from a single-lens light curve and lasted for about 6 h. The deviation exhibits a pattern of a dip surrounded by weak bumps on both sides of the dip. The analysis of the lensing light curve indicates that the signal is produced by a low-mass-ratio (q ~ 4 × 10−5) planetary companion located near the Einstein ring of the host star. Results. The mass of the planet, Mplanet = 6.8−3.5+4.7 M⊕ and 5.6−2.8+3.8 M⊕ for the two possible solutions, estimated from the Bayesian analysis indicates that the planet is in the regime of a super-Earth. The host of the planet is a disk star with a mass of Mhost = 0.47−0.25+0.33 M⊙ and a distance of DL = 4.2−.14+1.8 kpc. KMT-2018-BLG-1988Lb is the 18th known microlensing planet with a mass below the upper limit of a super-Earth. The fact that 15 out of the 18 known microlensing planets with masses ≲10 M⊕ were detected in the 5 yr following the full operation of the KMTNet survey indicates that the KMTNet database is an important reservoir of very low-mass planets.