The gravitational microlensing technique is most sensitive to planets in a Jupiterlike orbit and has detected more than 200 planets. However, only a few wideorbit (
Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher.
Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?
Some links on this page may take you to nonfederal websites. Their policies may differ from this site.

Abstract s > 2) microlensing planets have been discovered, wheres is the planettohost separation normalized to the angular Einstein ring radius,θ _{E}. Here, we present the discovery and analysis of a strong candidate wideorbit microlensing planet in the event OGLE2017BLG0448. The whole light curve exhibits longterm residuals to the static binarylens singlesource model, so we investigate the residuals by adding the microlensing parallax, microlensing xallarap, an additional lens, or an additional source. For the first time, we observe a complex degeneracy between all four effects. The wideorbit models withs ∼ 2.5 and a planettohost mass ratio ofq ∼ 10^{−4}are significantly preferred, but we cannot rule out the close models withs ∼ 0.35 andq ∼ 10^{−3}. A Bayesian analysis based on a Galactic model indicates that, despite the complicated degeneracy, the surviving wideorbit models all contain a superEarthmass to Neptunemass planet at a projected planethost separation of ∼6 au and the surviving closeorbit models all consist of a Jovianmass planet at ∼1 au. The host star is probably an M or K dwarf. We discuss the implications of this dimensiondegeneracy disaster on microlensing lightcurve analysis and its potential impact on statistical studies. 
Abstract We measure the Einstein radius of the singlelens microlensing event KMT2022BLG2397 to be
θ _{E}= 24.8 ± 3.6μ as, placing it at the upper shore of the Einstein Desert, 9 ≲θ _{E}/μ as ≲ 25, between freefloating planets (FFPs) and bulge brown dwarfs (BDs). In contrast to the six BD (25 ≲θ _{E}≲ 50) events presented by Gould et al. (2022), which all had giantstar source stars, KMT2022BLG2397 has a dwarfstar source, with angular radiusθ _{ast}∼ 0.9μ as. This prompts us to study the relative utility of dwarf and giant sources for characterizing FFPs and BDs from finitesource pointlens (FSPL) microlensing events. We find “dwarfs” (including mainsequence stars and subgiants) are likely to yield twice as manyθ _{E}measurements for BDs and a comparable (but more difficult to quantify) improvement for FFPs. We show that neither current nor planned experiments will yield complete mass measurements of isolated bulge BDs, nor will any other planned experiment yield as manyθ _{E}measurements for these objects as the Korea Microlensing Telescope (KMT). Thus, the currently anticipated 10 yr KMT survey will remain the best way to study bulge BDs for several decades to come. 
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

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

Abstract We report on the discovery and analysis of the planetary microlensing event OGLE2019BLG1180 with a planettostar mass ratio
q ∼ 0.003. The event OGLE2019BLG1180 has unambiguous cusppassing and causticcrossing anomalies, which were caused by a wide planetary caustic withs ≃ 2, wheres is the star–planet separation in units of the angular Einstein radiusθ _{E}. Thanks to wellcovered anomalies by the Korea Micorolensing Telescope Network (KMTNet), we measure both the angular Einstein radius and the microlens parallax in spite of a relatively short event timescale oft _{E}= 28 days. However, because of a weak constraint on the parallax, we conduct a Bayesian analysis to estimate the physical lens parameters. We find that the lens system is a superJupitermass planet of orbiting a latetype star of ${M}_{\mathrm{p}}={1.75}_{0.51}^{+0.53}\phantom{\rule{0.25em}{0ex}}{M}_{\mathrm{J}}$ at a distance ${M}_{\mathrm{h}}={0.55}_{0.26}^{+0.27}\phantom{\rule{0.25em}{0ex}}{M}_{\odot}$ . The projected star–planet separation is ${D}_{\mathrm{L}}={6.1}_{1.3}^{+0.9}\phantom{\rule{0.25em}{0ex}}\mathrm{kpc}$ , which means that the planet orbits at about four times the snow line of the host star. Considering the relative lens–source proper motion of ${a}_{\perp}={5.19}_{1.23}^{+0.90}\phantom{\rule{0.25em}{0ex}}\mathrm{au}$μ _{rel}= 6 mas yr^{−1}, the lens will be separated from the source by 60 mas in 2029. At that time one can measure the lens flux from adaptive optics imaging of Keck or a nextgeneration 30 m class telescope. OGLE2019BLG1180Lb represents a growing population of wideorbit planets detected by KMTNet, so we also present a general investigation into prospects for further expanding the sample of such planets. 
ABSTRACT In this work, we update and develop algorithms for KMTNet tenderlove care (TLC) photometry in order to create a new, mostly automated, TLC pipeline. We then start a project to systematically apply the new TLC pipeline to the historic KMTNet microlensing events, and search for buried planetary signals. We report the discovery of such a planet candidate in the microlensing event MOA2019BLG421/KMT2019BLG2991. The anomalous signal can be explained by either a planet around the lens star or the orbital motion of the source star. For the planetary interpretation, despite many degenerate solutions, the planet is most likely to be a Jovian planet orbiting an M or K dwarf, which is a typical microlensing planet. The discovery proves that the project can indeed increase the sensitivity of historic events and find previously undiscovered signals.

Aims. We investigate the microlensing data collected during the 2017–2019 seasons in the peripheral Galactic bulge fields with the aim of finding planetary signals in microlensing light curves observed with relatively sparse coverage. Methods. We first sort out lensing events with weak shortterm anomalies in the lensing light curves from the visual inspection of all nonprimefield events, and then test various interpretations of the anomalies. From this procedure, we find two previously unidentified candidate planetary lensing events KMT2017BLG0673 and KMT2019BLG0414. It is found that the planetary signal of KMT2017BLG0673 was produced by the source crossing over a planetinduced caustic, but it was previously missed because of the sparse coverage of the signal. On the other hand, the possibly planetary signal of KMT2019BLG0414 was generated without caustic crossing, and it was previously missed due to the weakness of the signal. We identify a unique planetary solution for KMT2017BLG0673. However, for KMT2019BLG0414, we identify two pairs of planetary solutions, for each of which there are two solutions caused by the closewide degeneracy, and a slightly less favored binarysource solution, in which a single lens mass gravitationally magnified a rapidly orbiting binary source with a faint companion (xallarap). Results. From Bayesian analyses, it is estimated that the planet KMT2017BLG0673Lb has a mass of 3.7 −2.1 +2.2 M J , and it is orbiting a late Ktype host star with a mass of 0.63 −0.35 +0.37 M ⊙ . Under the planetary interpretation of KMT2010BLG0414L, a star with a mass of 0.74 −0.38 +0.43 M ⊙ hosts a planet with a mass of ~3.2–3.6 M J depending on the solution. We discuss the possible resolution of the planetxallarap degeneracy of KMT2019BLG0414 by future adaptiveoptics observations on 30 m class telescopes. The detections of the planets indicate the need for thorough investigations of nonprimefield lensing events for the complete census of microlensing planet samples.more » « less

Aims. The light curve of the microlensing event KMT2021BLG0240 exhibits a shortlasting anomaly with complex features near the peak at the 0.1 mag level from a singlelens singlesource model. We conducted modeling of the lensing light curve under various interpretations to reveal the nature of the anomaly. Methods. It is found that the anomaly cannot be explained with the usual model based on a binarylens (2L1S) or a binarysource (1L2S) interpretation. However, a 2L1S model with a planet companion can describe part of the anomaly, suggesting that the anomaly may be deformed by a tertiary lens component or a close companion to the source. From the additional modeling, we find that all the features of the anomaly can be explained with either a triplelens (3L1S) model or a binarylens binarysource (2L2S) model. However, it is difficult to validate the 2L2S model because the light curve does not exhibit signatures induced by the source orbital motion and the ellipsoidal variations expected by the close separation between the source stars according to the model. We, therefore, conclude that the two interpretations cannot be distinguished with the available data, and either can be correct. Results. According to the 3L1S solution, the lens is a planetary system with two subJovianmass planets in which the planets have masses of 0.32–0.47 M J and 0.44–0.93 M J , and they orbit an M dwarf host. According to the 2L2S solution, on the other hand, the lens is a single planet system with a mass of ~0.21 M J orbiting a late Kdwarf host, and the source is a binary composed of a primary of a subgiant or a turnoff star and a secondary of a late G dwarf. The distance to the planetary system varies depending on the solution: ~7.0 kpc according to the 3L1S solution and ~6.6 kpc according to the 2L2S solution.more » « less

Abstract We present the analysis of seven microlensing planetary events with planet/host mass ratios q < 10 −4 : KMT2017BLG1194, KMT2017BLG0428, KMT2019BLG1806, KMT2017BLG1003, KMT2019BLG1367, OGLE2017BLG1806, and KMT2016BLG1105. They were identified by applying the Korea Microlensing Telescope Network (KMTNet) AnomalyFinder algorithm to 2016–2019 KMTNet events. A Bayesian analysis indicates that all the lens systems consist of a cold superEarth orbiting an M or K dwarf. Together with 17 previously published and three that will be published elsewhere, AnomalyFinder has found a total of 27 planets that have solutions with q < 10 −4 from 2016–2019 KMTNet events, which lays the foundation for the first statistical analysis of the planetary massratio function based on KMTNet data. By reviewing the 27 planets, we find that the missing planetary caustics problem in the KMTNet planetary sample has been solved by AnomalyFinder. We also find a desert of highmagnification planetary signals ( A ≳ 65), and a followup project for KMTNet highmagnification events could detect at least two more q < 10 −4 planets per year and form an independent statistical sample.more » « less

Aims. The light curve of the microlensing event KMT2021BLG1898 exhibits a shortterm central anomaly with doublebump features that cannot be explained by the usual binarylens or binarysource interpretations. With the aim of interpreting the anomaly, we analyze the lensing light curve under various sophisticated models. Methods. We find that the anomaly is explained by a model, in which both the lens and source are binaries (2L2S model). For this interpretation, the lens is a planetary system with a planet/host mass ratio of q ~ 1.5 × 10 −3 , and the source is a binary composed of a turn off or a subgiant star and a mid K dwarf. The doublebump feature of the anomaly can also be depicted by a triplelens model (3L1S model), in which the lens is a planetary system containing two planets. Among the two interpretations, the 2L2S model is favored over the 3L1S model not only because it yields a better fit to the data, by ∆ χ 2 = [14.3−18.5], but also the Einstein radii derived independently from the two stars of the binary source result in consistent values. According to the 2L2S interpretation, KMT2021BLG1898 is the third planetary lensing event occurring on a binary stellar system, following MOA2010BLG117 and KMT2018BLG1743. Results. Under the 2L2S interpretation, we identify two solutions resulting from the closewide degeneracy in determining the planethost separation. From a Bayesian analysis, we estimate that the planet has a mass of ~0.7−0.8 M J , and it orbits an early M dwarf host with a mass of ~0.5 M ⊙ . The projected planethost separation is ~1.9 AU and ~3.0 AU according to the close and wide solutions, respectively.more » « less