One Planet or Two Planets? The Ultra-sensitive Extreme-magnification Microlensing Event KMT-2019-BLG-1953
Cheongho Han, Doeon Kim, Youn Kil Jung, Andrew Gould, Ian A. Bond, Michael D. Albrow, Sun-Ju Chung, Kyu-Ha Hwang, Chung-Uk Lee, Yoon-Hyun Ryu, In-Gu Shin, Yossi… 展开作者
Cheongho Han, Doeon Kim, Youn Kil Jung, Andrew Gould, Ian A. Bond, Michael D. Albrow, Sun-Ju Chung, Kyu-Ha Hwang, Chung-Uk Lee, Yoon-Hyun Ryu, In-Gu Shin, Yossi Shvartzvald, Jennifer C. Yee, Weicheng Zang, Sang-Mok Cha, Dong-Jin Kim, Hyoun-Woo Kim, Seung-Lee Kim, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, Woong-Tae Kim, Fumio Abe, Richard Barry, David P. Bennett, Aparna Bhattacharya, Martin Donachie, Hirosane Fujii, Akihiko Fukui, Yoshitaka Itow, Yuki Hirao, Rintaro Kirikawa, Iona Kondo, Naoki Koshimoto, Man Cheung Alex Li, Yutaka Matsubara, Yasushi Muraki, Shota Miyazaki, Masayuki Nagakane, Clément Ranc, Nicholas J. Rattenbury, Yuki Satoh, Hikaru Shoji, Haruno Suematsu, Takahiro Sumi, Daisuke Suzuki, Yuzuru Tanaka, Paul J. Tristram, Tsubasa Yamawaki, Atsunori Yonehara
We present the analysis of a very high-magnification ($A\sim 900$) microlensing event KMT-2019-BLG-1953. A single-lens single-source (1L1S) model appears to approximately delineate the observed light curve, but the residuals from the model exhibit small but obvious deviations in the peak region. A binary lens (2L1S) model with a mass ratio $q\sim 2\times 10^{-3}$ improves the fits by $Δχ^2=181.8$, indicating that the lens possesses a planetary companion. From additional modeling by introducing an extra planetary lens component (3L1S model) and an extra source companion (2L2S model), it is found that the residuals from the 2L1S model further diminish, but claiming these interpretations is difficult due to the weak signals with $Δχ^2=16.0$ and $13.5$ for the 3L1S and 2L2L models, respectively. From a Bayesian analysis, we estimate that the host of the planets has a mass of $M_{\rm host}=0.31^{+0.37}_{-0.17}~M_\odot$ and that the planetary system is located at a distance of $D_{\rm L}=7.04^{+1.10}_{-1.33}~{\rm kpc}$ toward the Galactic center. The mass of the securely detected planet is $M_{\rm p}=0.64^{+0.76}_{-0.35}~M_{\rm J}$. The signal of the potential second planet could have been confirmed if the peak of the light curve had been more densely observed by followup observations, and thus the event illustrates the need for intensive followup observations for very high-magnification events even in the current generation of high-cadence surveys.
Testing KMTNet--PRIME Optical--Near-Infrared Source-Color Constraints in KMT-2024-BLG-0211 and KMT-2024-BLG-1522
The University of Osaka（大阪大学）；Massey University（梅西大学）；Ohio State University（俄亥俄州立大学）；Westlake University（西湖大学）；NASA Goddard Space Flight Center（美国宇航局戈达德太空飞行中心）；University of Maryland, College Park（马里兰大学帕克分校）
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. We first sort out lensing events with weak short-term anomalies in the lensing light curves from the visual inspection of all non-prime-field events, and then test various interpretations of the anomalies. From this procedure, we find two previously unidentified candidate planetary lensing events KMT-2017-BLG-0673 and KMT-2019-BLG-0414. It is found that the planetary …
We systematically inspect 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 binary-lens or binary-source interpretations. From the inspection, we find that interpreting the three lensing events OGLE-2018-BLG-0584, KMT-2018-BLG-2119, and KMT-2021-BLG-1122 requires four-body (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 …
KMT-2025-BLG-1314 and KMT-2025-BLG-1392: two microlensing planetary/brown-dwarf candidates analyzed with differentiable code
Tsinghua University（清华大学）；Westlake University（西湖大学）；Korea Astronomy and Space Science Institute（韩国天文与空间科学研究院）；University of Canterbury（坎特伯雷大学）；Max-Planck-Institute for Astronomy（马克斯·普朗克天文学研究所）；Ohio State University（俄亥俄州立大学）；Chungbuk National University（忠北国立大学）；National University of Science and Technology (UST)（韩国科学技术院）
KMT-2025-BLG-0975Lb and KMT-2025-BLG-1160Lb: Two Uranus-Mass Planets Beyond the Snow Line Discovered by Microlensing
Chungbuk National University（忠北国立大学）；Korea Astronomy and Space Science Institute（韩国天体宇宙科学研究所）；University of Warsaw（华沙大学）；Ohio State University（俄亥俄州立大学）；University of Canterbury（坎特伯雷大学）；University of Science and Technology（科学技术大学）
We present the analysis of seven microlensing planetary events with planet/host mass ratios $q < 10^{-4}$: KMT-2017-BLG-1194, KMT-2017-BLG-0428, KMT-2019-BLG-1806, KMT-2017-BLG-1003, KMT-2019-BLG-1367, OGLE-2017-BLG-1806, and KMT-2016-BLG-1105. 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 super-Earth orbiting an M or K dwarf. Together with 17 previously published and three that will be published elsewhere, AnomalyFinder has found a…
We present the analysis of three more planets from the KMTNet 2021 microlensing season. KMT-2021-BLG-0119Lb is a $\sim 6\, M_{\rm Jup}$ planet orbiting an early M-dwarf or a K-dwarf, KMT-2021-BLG-0192Lb is a $\sim 2\, M_{\rm Nep}$ planet orbiting an M-dwarf, and KMT-2021-BLG-0192Lb is a $\sim 1.25\, M_{\rm Nep}$ planet orbiting a very--low-mass M dwarf or a brown dwarf. These by-eye planet detections provide an important comparison sample to the sample selected with the AnomalyFinder algorithm, and in particular, KMT-2021-BLG-2294, is a case of a planet detected by-eye but not by-algorithm. KM…
Follow-up observations of high-magnification gravitational microlensing events can fully exploit their intrinsic sensitivity to detect extrasolar planets, especially those with small mass ratios. To make followup more uniform and efficient, we develop a system, HighMagFinder, based on the real-time data from the Korean Microlensing Telescope Network (KMTNet) to automatically alert possible ongoing high-magnification events. We started a new phase of follow-up observations with the help of HighMagFinder in 2021. Here we report the discovery of two planets in high-magnification microlensing even…
We continue our program of publishing all planets (and possible planets) found by eye in 2021 Korea Microlensing Telescope Network (KMTNet) online data. We present 4 planets, (KMT-2021-BLG-0712Lb, KMT-2021-BLG-0909Lb, KMT-2021-BLG-2478Lb, and KMT-2021-BLG-1105Lb), with planet-host mass ratios in the range -3.3 < log q < -2.2. This brings the total of secure, by-eye, 2021 KMTNet planets to 16, including 8 in this series. The by-eye sample is an important check of the completeness of semi-automated detections, which are the basis for statistical analyses. One of the planets, KMT-2021-BLG-1105Lb,…
KMT-2024-BLG-0816/OGLE-2024-BLG-0519 -- A Microlensing Event with Candidate Free-Floating Planet Lens and Blended Light
University of Warsaw（华沙大学）；Korea Astronomy and Space Science Institute（韩国天文学与空间科学研究所）；Westlake University（西湖大学）；University of Canterbury（坎特伯雷大学）；Max-Planck-Institute for Astronomy（马克斯·普朗克天体物理学研究所）；Ohio State University（俄亥俄州立大学）；Chungbuk National University（忠北国立大学）；National University of Science and Technology (UST)（国立科学技术大学）；Weizmann Institute of Science（魏茨曼科学研究所）
We complete the analysis of all 2018 sub-prime-field microlensing planets identified by the KMTNet AnomalyFinder. Among the 9 previously unpublished events with clear planetary solutions, 6 are clearly planetary (KMT-2018-BLG-0030, KMT-2018-BLG-0087, KMT-2018-BLG-0247, OGLE-2018-BLG-0298, KMT-2018-BLG-2602, and OGLE-2018-BLG-1119), while the remaining 3 are ambiguous in nature. In addition, there are 8 previously published sub-prime field planets that were selected by the AnomalyFinder algorithm. Together with a companion paper (Gould et al. 2022) on 2018 prime-field planets, this work lays th…
We conduct a systematic investigation of the microlensing data collected during the previous observation seasons for the purpose of reanalyzing anomalous lensing events with no suggested plausible models. We find that two anomalous lensing events OGLE-2018-BLG-0584 and KMT-2018-BLG-2119 cannot be explained with the usual models based on either a binary-lens single-source (2L1S) or a single-lens binary-source (1L2S) interpretation. We test the feasibility of explaining the light curves with more sophisticated models by adding an extra lens (3L1S model) or a source (2L2S model) component to the …
Candidate Microlensing Brown Dwarfs in Binary Lens Systems from the 2023--2025 Observing Seasons
Chungbuk National University（忠北国立大学）；University of Warsaw（华沙大学）；Massey University（梅西大学）；Korea Astronomy and Space Science Institute（韩国天文学与空间科学研究所）；University of Canterbury（坎特伯雷大学）；Ohio State University（俄亥俄州立大学）；University of Science and Technology（科学技术大学）
We present the analysis of KMT-2016-BLG-0212, a low flux-variation $(I_{\rm flux-var}\sim 20$) microlensing event, which is well-covered by high-cadence data from the three Korea Microlensing Telescope Network (KMTNet) telescopes. The event shows a short anomaly that is incompletely covered due to the brief visibility intervals that characterize the early microlensing season when the anomaly occurred. We show that the data are consistent with two classes of solutions, characterized respectively by low-mass brown-dwarf $(q=0.037)$ and sub-Neptune $(q<10^{-4})$ companions, respectively. Future h…
As a part of the ``Systematic KMTNet Planetary Anomaly Search" series, we report five new planets (namely, OGLE-2016-BLG-1635Lb, MOA-2016-BLG-532Lb, KMT-2016-BLG-0625Lb, OGLE-2016-BLG-1850Lb, and KMT-2016-BLG-1751Lb) and one planet candidate (KMT-2016-BLG-1855), which were found by searching $2016$ KMTNet prime fields. These $buried$ planets show a wide range of masses from Earth--class to Super--Jupiter--class, and are located in both the disk and the bulge. The ultimate goal of this series is to build a complete planet sample. Because our work provides a complementary sample to other planet …
We complete the analysis of all 2018 prime-field microlensing planets identified by the KMTNet AnomalyFinder. Among the 10 previously unpublished events with clear planetary solutions, 8 are either unambiguously planetary or are very likely to be planetary in nature: OGLE-2018-BLG-1126, KMT-2018-BLG-2004, OGLE-2018-BLG-1647, OGLE-2018-BLG-1367, OGLE-2018-BLG-1544, OGLE-2018-BLG-0932, OGLE-2018-BLG-1212, and KMT-2018-BLG-2718. Combined with the 4 previously published new AnomalyFinder events and 12 previously published (or in preparation) planets that were discovered by eye, thismakes a total o…
KMT-2016-BLG-2605, with planet-host mass ratio $q=0.012\pm 0.001$, has the shortest Einstein timescale, $t_\e = 3.41\pm 0.13\,$days, of any planetary microlensing event to date. This prompts us to examine the full sample of 7 short ($t_\e<7\,$day) planetary events with good $q$ measurements. We find that six have clustered Einstein radii $θ_\e = 115\pm 20\,\muas$ and lens-source relative proper motions $μ_\rel\simeq 9.5\pm 2.5\,\masyr$. For the seventh, these two quantities could not be measured. These distributions are consistent with a Galactic-bulge population of very low-mass (VLM) hosts n…
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 that was found from this investigation. The planetary signal appears as a deviation with $\lesssim 0.2$~mag from a single-lens light curve and lasted for about 6 hours. 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 …
Mass Production of 2023 KMTNet Microlensing Planets I: Low Mass Ratio
Korea Astronomy and Space Science Institute（韩国天文与空间科学研究所）；Astronomical Observatory, University of Warsaw（华沙大学天文台）；Westlake University（西湖大学）；Tsinghua University（清华大学）；University of Chinese Academy of Sciences（中国科学院大学）；Ohio State University（俄亥俄州立大学）；University of Canterbury（坎特伯雷大学）
We report the discovery and characterization of KMT-2018-BLG-1990Lb, a Jovian planet $(m_p=0.57_{-0.25}^{+0.79}\,M_J)$ orbiting a late M dwarf $(M=0.14_{-0.06}^{+0.20}\,M_\odot)$, at a distance $(D_L=1.23_{-0.43}^{+1.06}\,\kpc)$, and projected at $2.6\pm 0.6$ times the snow line distance, i.e., $a_{\rm snow}\equiv 2.7\,\au (M/M_\odot)$, This is the second Jovian planet discovered by KMTNet in its low cadence ($0.4\,{\rm hr}^{-1}$) fields, demonstrating that this population will be well characterized based on survey-only microlensing data.
With the aim of finding short-term planetary signals, we investigated the data collected from the high-cadence microlensing surveys. From this investigation, we found four planetary systems with low planet-to-host mass ratios, including OGLE-2017-BLG-1691L, KMT-2021-BLG-0320L, KMT-2021-BLG-1303L, and KMT-2021-BLG-1554L. Despite the short durations, ranging from a few hours to a couple of days, the planetary signals were clearly detected by the combined data of the lensing surveys. It is found that three of the planetary systems have mass ratios of the order of $10^{-4}$ and the other has a mas…
We report the discovery of an extrasolar planet detected from the combined data of a microlensing event OGLE-2015-BLG-0051/KMT-2015-BLG-0048 acquired by two microlensing surveys. Despite that the short planetary signal occurred in the very early Bulge season during which the lensing event could be seen for just about an hour, the signal was continuously and densely covered. From the Bayesian analysis using models of the mass function, matter and velocity distributions combined with the information of the angular Einstein radius, it is found that the host of the planet is located in the Galacti…
Mass Production of 2023 KMTNet Microlensing Planets. II: Two Planets and A Brown Dwarf
Westlake University（西湖大学）；Tsinghua University（清华大学）；Korea Astronomy and Space Science Institute（韩国天体宇宙科学研究所）；Astronomical Observatory, University of Warsaw（华沙大学天文台）；Department of Earth and Space Science, Graduate School of Science, Osaka University（大阪大学理学研究科地球・宇宙科学系）；University of Canterbury, School of Physical and Chemical Sciences（坎特伯雷大学物理与化学科学学院）
Limits on a Host Star around a Saturn-mass Free-floating Planet Candidate KMT-2024-BLG-0792/OGLE-2024-BLG-0516
University of Warsaw（华沙大学）；École Normale Supérieure, Paris（巴黎高等师范学院）；European Southern Observatory（欧洲南方天文台）；Peking University（北京大学）；National Astronomical Observatories, Chinese Academy of Science（中国科学院国家天文台）
We analyze the very short Einstein timescale ($t_\rm E \simeq 7\,{\rm hr}$) event KMT-2019-BLG-2073. Making use of the pronounced finite-source effects generated by the clump-giant source, we measure the Einstein radius $θ_\rm E \simeq 4.8\,\rm μas$, and so infer a mass $M = 59\,M_\oplus (π_\rm{rel}/16 \,\rm μas)^{-1}$, where $π_\rm{rel}$ is the lens-source relative parallax. We find no significant evidence for a host of this planetary mass object, though one could be present at sufficiently wide separation. If so, it would be detectable after about 10 years. This is the fourth isolated microl…
KMT-2025-BLG-2093: Free-Floating Planet Candidate Near the Shore of the Einstein Desert
Korea Astronomy and Space Science Institute（韩国天体宇宙科学研究所）；Ohio State University（俄亥俄州立大学）；Westlake University（西湖大学）；Tsinghua University（清华大学）；University of Canterbury（坎特伯雷大学）；Chungbuk National University（忠北国立大学）；National University of Science and Technology (UST)（韩国科学技术院）；Weizmann Institute of Science（魏茨曼科学研究所）
We report the discovery of a giant planet in the KMT-2016-BLG-1397 microlensing event, which was found by The Korea Microlensing Telescope Network (KMTNet) alone. The time scale of this event is t_E = 40.0 +- 0.5 days and the mass ratio between the lens star and its companion is q = 0.016 +- 0.002. The planetary perturbation in the light curve is a smooth bump, resulting in the classical binary-lens/binary-source (2L1S/1L2S) degeneracy. We measure the V - I color of the (putative) two sources in the 1L2S model, and then effectively rule out the binary source solution. The finite-source effect …
We investigate the microlensing event KMT-2021-BLG-0322, for which the light curve exhibits three distinctive sets of caustic-crossing features. It is found that the overall features of the light curve are approximately described by a binary-lens (2L1S) model, but the model leaves substantial residuals. We test various interpretations with the aim of explaining the residuals. We find that the residuals can be explained either by considering a nonrectilinear lens-source motion caused by the microlens-parallax and lens-orbital effects or by adding a low-mass companion to the binary lens (3L1S mo…
We analyze KMT-2019-BLG-1339, a microlensing event with an obvious but incompletely resolved brief anomaly feature around the peak of the light curve. Although the origin of the anomaly is identified to be a companion to the lens with a low mass ratio $q$, the interpretation is subject to two different degeneracy types. The first type is the ambiguity in $ρ$, representing the angular source radius scaled to the angular radius of the Einstein ring, $θ_{\rm E}$, and the other is the $s\leftrightarrow s^{-1}$ degeneracy. The former type, `finite-source degeneracy', causes ambiguities in both $s$ …
The high-magnification microlensing event KMT-2021-BLG-1077 exhibits a subtle and complex anomaly pattern in the region around the peak. We analyze the lensing light curve of the event with the aim of revealing the nature of the anomaly. We test various models in combination with several interpretations. We find that the anomaly cannot be explained by the usual three-body (2L1S and 1L2S) models. The 2L2S model improves the fit compared to the three-body models, but it still leaves noticeable residuals. On the other hand, the 3L1S interpretation yields a model explaining all the major anomalous…
The light curve of the microlensing event KMT-2021-BLG-1898 exhibits a short-term central anomaly with double-bump features that cannot be explained by the usual binary-lens or binary-source interpretations. With the aim of interpreting the anomaly, we analyze the lensing light curve under various sophisticated models. 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 $q\sim 1.5\times 10^{-3}$, and the source is a binary composed of a turn off or…
We search for microlensing planets with signals exhibiting no caustic-crossing features, considering the possibility that such signals may be missed due to their weak and featureless nature. For this purpose, we reexamine the lensing events found by the KMTNet survey before the 2019 season. From this investigation, we find two new planetary lensing events, KMT-2018-BLG-1976 and KMT-2018-BLG-1996. We also present the analysis of the planetary event OGLE-2019-BLG-0954, for which the planetary signal was known, but no detailed analysis has been presented before. We identify the genuineness of the…
We announce the discovery of a microlensing planetary system, in which a sub-Saturn planet is orbiting an ultracool dwarf host. We detect the planetary system by analyzing the short-timescale ($t_{\rm E}\sim 4.4$~days) lensing event KMT-2018-BLG-0748. The central part of the light curve exhibits asymmetry due to the negative deviations in the rising part and the positive deviations in the falling part. We find that the deviations are explained by a binary-lens model with a mass ratio between the lens components of $q\sim 2\times 10^{-3}$. The short event timescale together with the small angul…
We investigate the gravitational microlensing event KMT-2019-BLG-1715, of which light curve shows two short-term anomalies from a caustic-crossing binary-lensing light curve: one with a large deviation and the other with a small deviation. We identify five pairs of solutions, in which the anomalies are explained by adding an extra lens or source component in addition to the base binary-lens model. We resolve the degeneracies by applying a method, in which the measured flux ratio between the first and second source stars is compared with the flux ratio deduced from the ratio of the source radii…
We present the analysis of the microlensing event KMT-2018-BLG-1743. The light curve of the event, with a peak magnification $A_{\rm peak}\sim 800$, 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 …
We report a new free-floating planet (FFP) candidate, KMT-2017-BLG-2820, with Einstein radius $θ_\e\simeq 6\,\muas$, lens-source relative proper motion $μ_\rel \simeq 8\,\masyr$, and Einstein timescale $t_\e=6.5\,$hr. It is the third FFP candidate found in an ongoing study of giant-source finite-source point-lens (FSPL) events in the KMTNet data base, and the sixth FSPL FFP candidate overall. We find no significant evidence for a host. Based on their timescale distributions and detection rates, we argue that five of these six FSPL FFP candidates are drawn from the same population as the six po…
We report the discovery of a super-Jovian planet in the microlensing event KMT-2016-BLG-1836, which was found by the Korea Microlensing Telescope Network's high-cadence observations (Γ~ 4~{hr}^{-1}). The planet-host mass ratio q ~ 0.004. A Bayesian analysis indicates that the planetary system is composed of a super-Jovian M_{planet} = 2.2_{-1.1}^{+1.9} M_{J} planet orbiting an M or K dwarf M_{\rm host} = 0.49_{-0.25}^{+0.38} M_{Sun}, at a distance of D_{L} = 7.1_{-2.4}^{+0.8} kpc. The projected planet-host separation is 3.5^{+1.1}_{-0.9} AU, implying that the planet is located beyond the snowl…
We report two microlensing events, KMT-2017-BLG-1038 and KMT-2017-BLG-1146 that are caused by planetary systems. These events were discovered by KMTNet survey observations from the $2017$ bulge season. The discovered systems consist of a planet and host star with mass ratios, $5.3_{-0.4}^{+0.2} \times 10^{-3}$ and $2.0_{-0.1}^{+0.6} \times 10^{-3}$, respectively. Based on a Bayesian analysis assuming a Galactic model without stellar remnant hosts, we find that the planet, KMT-2017-BLG-1038Lb, is a super Jupiter-mass planet ($M_{\rm p}= 2.04_{-1.15}^{+2.02}\,M_{\rm J}$) orbiting a mid-M dwarf h…
Only a few wide-orbit planets around old stars have been detected, which limits our statistical understanding of this planet population. Following the systematic search for planetary anomalies in microlensing events found by the Korea Microlensing Telescope Network (KMTNet), we present the discovery and analysis of three events that were initially thought to contain wide-orbit planets. The anomalous feature in the light curve of OGLE-2018-BLG-0383 is caused by a planet with mass ratio $q=2.1\times 10^{-4}$ and a projected separation $s=2.45$. This makes it the lowest mass-ratio microlensing pl…
