We complete the publication of all microlensing planets (and “possible planets”) identified by the uniform approach of the KMT AnomalyFinder system in the 21 KMT subprime fields during the 2019 observing season, namely, KMT2019BLG0298, KMT2019BLG1216, KMT2019BLG2783, OGLE2019BLG0249, and OGLE2019BLG0679 (planets), as well as OGLE2019BLG0344 and KMT2019BLG0304 (possible planets). The five planets have mean log mass ratio measurements of (−2.6, −3.6, −2.5, −2.2, −2.3), median mass estimates of (1.81, 0.094, 1.16, 7.12, 3.34)
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Abstract M _{Jup}, and median distance estimates of (6.7, 2.7, 5.9, 6.4, 5.6) kpc, respectively. The main scientific interest of these planets is that they complete the AnomalyFinder sample for 2019, which has a total of 25 planets that are likely to enter the statistical sample. We find statistical consistency with the previously published 33 planets from the 2018 AnomalyFinder analysis according to an ensemble of five tests. Of the 58 planets from 2018–2019, 23 were newly discovered by AnomalyFinder. Within statistical precision, half of the planets have caustic crossings, while half do not; an equal number of detected planets result from major and minorimage lightcurve perturbations; and an equal number come from KMT prime fields versus subprime fields. 
Abstract We present the analysis of three more planets from the KMTNet 2021 microlensing season. KMT2021BLG0119Lb is a ∼6
M _{Jup}planet orbiting an early M dwarf or a K dwarf, KMT2021BLG0192Lb is a ∼2M _{Nep}planet orbiting an M dwarf, and KMT2021BLG2294Lb is a ∼1.25M _{Nep}planet orbiting a verylowmass M dwarf or a brown dwarf. These byeye planet detections provide an important comparison sample to the sample selected with the AnomalyFinder algorithm, and in particular, KMT2021BLG2294 is a case of a planet detected by eye but not by algorithm. KMT2021BLG2294Lb is part of a population of microlensing planets around verylowmass host stars that spans the full range of planet masses, in contrast to the planet population at ≲0.1 au, which shows a strong preference for small planets. 
ABSTRACT We report the complete statistical planetary sample from the prime fields (Γ ≥ 2 h−1) of the 2019 Korea Microlensing Telescope Network (KMTNet) microlensing survey. We develop the optimized KMTNet AnomalyFinder algorithm and apply it to the 2019 KMTNet prime fields. We find a total of 13 homogeneously selected planets and report the analysis of three planetary events, KMT2019BLG(1042,1552,2974). The planet–host mass ratios, q, for the three planetary events are 6.34 × 10−4, 4.89 × 10−3, and 6.18 × 10−4, respectively. A Bayesian analysis indicates the three planets are all cold giant planets beyond the snow line of their host stars. The 13 planets are basically uniform in log q over the range −5.0 < log q < −1.5. This result suggests that the planets below qbreak = 1.7 × 10−4 proposed by the MOAII survey may be more common than previously believed. This work is an early component of a large project to determine the KMTNet massratio function, and the whole sample of 2016–2019 KMTNet events should contain about 120 planets.

ABSTRACT Followup observations of highmagnification gravitational microlensing events can fully exploit their intrinsic sensitivity to detect extrasolar planets, especially those with small mass ratios. To make followup observations more uniform and efficient, we develop a system, HighMagFinder, to automatically alert possible ongoing highmagnification events based on the realtime data from the Korea Microlensing Telescope Network (KMTNet). We started a new phase of followup observations with the help of HighMagFinder in 2021. Here we report the discovery of two planets in highmagnification microlensing events, KMT2021BLG0171 and KMT2021BLG1689, which were identified by the HighMagFinder. We find that both events suffer the ‘centralresonant’ caustic degeneracy. The planethost massratio is q ∼ 4.7 × 10−5 or q ∼ 2.2 × 10−5 for KMT2021BLG0171, and q ∼ 2.5 × 10−4 or q ∼ 1.8 × 10−4 for KMT2021BLG1689. Together with two other events, four cases that suffer such degeneracy have been discovered in the 2021 season alone, indicating that the degenerate solutions may have been missed in some previous studies. We also propose a quantitative factor to weight the probability of each solution from the phase space. The resonant interpretations for the two events are disfavoured under this consideration. This factor can be included in future statistical studies to weight degenerate solutions.

Aims. We inspect the four microlensing events KMT2021BLG1968, KMT2021BLG2010, KMT2022BLG0371, and KMT2022BLG1013, for which the light curves exhibit partially covered shortterm central anomalies. We conduct detailed analyses of the events with the aim of revealing the nature of the anomalies. Methods. We tested various models that can explain the anomalies of the individual events, including the binarylens (2L1S) and binarysource (1L2S) interpretations. Under the 2L1S interpretation, we thoroughly inspected the parameter space to determine the existence of degenerate solutions, and if they existed, we tested whether the degeneracy could be resolved. Results. We find that the anomalies in KMT2021BLG2010 and KMT2022BLG1013 are uniquely defined by planetarylens interpretations with planettohost mass ratios of q ~ 2.8 × 10 −3 and ~1.6 × 10 −3 , respectively. For KMT2022BLG0371, a planetary solution with a mass ratio q ~ 4 × 10 −4 is strongly favored over the other three degenerate 2L1S solutions with different mass ratios based on the χ 2 and relative proper motion arguments, and a 1L2S solution is clearly ruled out. For KMT2021BLG1968, on the other hand, we find that the anomaly can be explained either by a planetary or a binarysource interpretation, making it difficult to firmly identify the nature of the anomaly. From the Bayesian analyses of the identified planetary events, we estimate that the masses of the planet and host are ( M p / M J , M h / M ⊙ ) = (1.07 −0.68 +1.15 , 0.37 −0.23 +0.40 ), (0.26 −0.11 +0.13 , 0.63 −0.28 +0.32 ), and (0.31 −0.16 +0.46 , 0.18 −0.10 +0.28 ) for KMT2021BLG2010L, KMT2022BLG0371L, and KMT2022BLG1013L, respectively.more » « less

Aims. We investigate the data collected by the highcadence microlensing surveys during the 2022 season in search of planetary signals appearing in the light curves of microlensing events. From this search, we find that the lensing event MOA2022BLG249 exhibits a brief positive anomaly that lasted for about one day, with a maximum deviation of ~0.2 mag from a singlesource, singlelens model. Methods. We analyzed the light curve under the two interpretations of the anomaly: one originated by a lowmass companion to the lens (planetary model) and the other originated by a faint companion to the source (binarysource model). Results. We find that the anomaly is better explained by the planetary model than the binarysource model. We identified two solutions rooted in the innerouter degeneracy and for both of them, the estimated planettohost mass ratio, q ~ 8 × 10 −5 , is very small. With the constraints provided by the microlens parallax and the lower limit on the Einstein radius, as well as the blendflux constraint, we find that the lens is a planetary system, in which a superEarth planet, with a mass of (4.83 ± 1.44) Μ ⊕ , orbits a lowmass host star, with a mass of (0.18 ± 0.05) M ⊙ , lying in the Galactic disk at a distance of (2.00 ± 0.42) kpc. The planet detection demonstrates the elevated microlensing sensitivity of the current highcadence lensing surveys to lowmass planets.more » « less

ABSTRACT We present the observations and analysis of a highmagnification microlensing planetary event, KMT2022BLG0440, for which the weak and shortlived planetary signal was covered by both the KMTNet survey and followup observations. The binarylens models with a central caustic provide the best fits, with a planet/host mass ratio, q = 0.75–1.00 × 10−4 at 1σ. The binarylens models with a resonant caustic and a browndwarf mass ratio are both excluded by Δχ2 > 70. The binarysource model can fit the anomaly well but is rejected by the ‘colour 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 disc, the planet probably has a Neptunemass, and the projected planethost separation is $1.9^{+0.6}_{0.7}$ or $4.6^{+1.4}_{1.7}$ au, subject to the close/wide degeneracy. This is the third q < 10−4 planet from a highmagnification planetary signal (A ≳ 65). Together with another such planet, KMT2021BLG0171Lb, the ongoing followup program for the KMTNet highmagnification events has demonstrated its ability to detect highmagnification planetary signals for q < 10−4 planets, which are challenging for the current microlensing surveys.more » « less

Aims. We systematically inspected the microlensing data acquired by the KMTNet survey during the previous seasons in order to find anomalous lensing events for which the anomalies in the lensing light curves cannot be explained by the usual binarylens or binarysource interpretations. Methods. From the inspection, we find that interpreting the three lensing events OGLE2018BLG0584, KMT2018BLG2119, and KMT2021BLG1122 requires fourbody (lens+source) models, in which either both the lens and source are binaries (2L2S event) or the lens is a triple system (3L1S event). Following the analyses of the 2L2S events presented in our previous work, here we present the 3L1S analysis of the KMT2021BLG1122. Results. It is found that the lens of the event KMT2021BLG1122 is composed of three masses, in which the projected separations (normalized to the angular Einstein radius) and mass ratios between the lens companions and the primary are ( s 2 , q 2 )∼(1.4, 0.53) and ( s 3 , q 3 )∼(1.6, 0.24). By conducting a Bayesian analysis, we estimate that the masses of the individual lens components are ( M 1 , M 2 , M 3 )∼(0.47 M ⊙ , 0.24 M ⊙ , 0.11 M ⊙ ). The companions are separated in projection from the primary by ( a ⊥, 2 , a ⊥, 3 )∼(3.5, 4.0) AU. The lens of KMT2018BLG2119 is the first triple stellar system detected via microlensing.more » « less

Abstract We analyze the MOA2020BLG208 gravitational microlensing event and present the discovery and characterization of a new planet, MOA2020BLG208Lb, with an estimated subSaturn mass. With a mass ratio q = 3.17 − 0.26 + 0.28 × 10 − 4 , the planet lies near the peak of the massratio function derived by the MOA collaboration and near the edge of expected sample sensitivity. For these estimates we provide results using two masslaw priors: one assuming that all stars have an equal planethosting probability, and the other assuming that planets are more likely to orbit around more massive stars. In the first scenario, we estimate that the lens system is likely to be a planet of mass m planet = 46 − 24 + 42 M ⊕ and a host star of mass M host = 0.43 − 0.23 + 0.39 M ⊙ , located at a distance D L = 7.49 − 1.13 + 0.99 kpc . For the second scenario, we estimate m planet = 69 − 34 + 37 M ⊕ , M host = 0.66 − 0.32 + 0.35 M ⊙ , and D L = 7.81 − 0.93 + 0.93 kpc . The planet has a projected separation as a fraction of the Einstein ring radius s = 1.3807 − 0.0018 + 0.0018 . As a cool subSaturnmass planet, this planet adds to a growing collection of evidence for revised planetary formation models.more » « less

ABSTRACT We present K22016BLG0005Lb, a densely sampled, planetary binary causticcrossing microlensing event found from a blind search of data gathered from Campaign 9 of the Kepler K2 mission (K2C9). K22016BLG0005Lb is the first bound microlensing exoplanet discovered from spacebased data. The event has caustic entry and exit points that are resolved in the K2C9 data, enabling the lenssource relative proper motion to be measured. We have fitted a binary microlens model to the Kepler data and to simultaneous observations from multiple groundbased surveys. Whilst the groundbased data only sparsely sample the binary caustic, they provide a clear detection of parallax that allows us to break completely the microlensing masspositionvelocity degeneracy and measure the planet’s mass directly. We find a host mass of 0.58 ± 0.04 M⊙ and a planetary mass of 1.1 ± 0.1 MJ. The system lies at a distance of 5.2 ± 0.2 kpc from Earth towards the Galactic bulge, more than twice the distance of the previous most distant planet found by Kepler. The skyprojected separation of the planet from its host is found to be 4.2 ± 0.3 au which, for circular orbits, deprojects to a host separation $a = 4.4^{+1.9}_{0.4}$ au and orbital period $P = 13^{+9}_{2}$ yr. This makes K22016BLG0005Lb a close Jupiter analogue orbiting a lowmass host star. According to current planet formation models, this system is very close to the host mass threshold below which Jupiters are not expected to form. Upcoming spacebased exoplanet microlensing surveys by NASA’s Nancy Grace Roman Space Telescope and, possibly, ESA’s Euclid mission, will provide demanding tests of current planet formation models.more » « less