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  • Han, Cheongho  (39)
  • Jung, Youn Kil  (39)
  • Physics  (39)
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  • Physics  (39)
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  • 1
    Online Resource
    Online Resource
    Three microlensing planets with no caustic-crossing features
    EDP Sciences ; 2021
    In:  Astronomy & Astrophysics Vol. 650 ( 2021-6), p. A89-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 650 ( 2021-6), p. A89-
    Abstract: Aims. 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. Methods. 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 had previously been presented. We identify the genuineness of the planetary signals by checking various interpretations that can generate short-term anomalies in lensing light curves. Results. From Bayesian analyses conducted with the constraint from available observables, we find that the host and planet masses are ( M 1 , M 2 ) ~ (0.65  M ⊙ , 2  M J ) for KMT-2018-BLG-1976L, ~(0.69  M ⊙ , 1  M J ) for KMT-2018-BLG-1996L, and ~(0.80  M ⊙ , 14  M J ) for OGLE-2019-BLG-0954L. The estimated distance to OGLE-2019-BLG-0954L, 3.63 −1.64 +1.22 kpc, indicates that it is located in the disk, and the brightness expected from the mass and distance matches the brightness of the blend well, indicating that the lens accounts for most of the blended flux. The lens of OGLE-2019-BLG-0954 may be resolved from the source by conducting high-resolution follow-up observations in and after 2024.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202140758
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2021
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 2
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    KMT-2017-BLG-0673Lb and KMT-2019-BLG-0414Lb: Two microlensing planets detected in peripheral fields of KMTNet survey
    EDP Sciences ; 2022
    In:  Astronomy & Astrophysics Vol. 666 ( 2022-10), p. A132-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 666 ( 2022-10), p. A132-
    Abstract: 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 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 signal of KMT-2017-BLG-0673 was produced by the source crossing over a planet-induced caustic, but it was previously missed because of the sparse coverage of the signal. On the other hand, the possibly planetary signal of KMT-2019-BLG-0414 was generated without caustic crossing, and it was previously missed due to the weakness of the signal. We identify a unique planetary solution for KMT-2017-BLG-0673. However, for KMT-2019-BLG-0414, we identify two pairs of planetary solutions, for each of which there are two solutions caused by the close-wide degeneracy, and a slightly less favored binary-source 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 KMT-2017-BLG-0673Lb has a mass of 3.7 −2.1 +2.2 M J , and it is orbiting a late K-type host star with a mass of 0.63 −0.35 +0.37 M ⊙ . Under the planetary interpretation of KMT-2010-BLG-0414L, 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 planet-xallarap degeneracy of KMT-2019-BLG-0414 by future adaptive-optics observations on 30 m class telescopes. The detections of the planets indicate the need for thorough investigations of non-prime-field lensing events for the complete census of microlensing planet samples.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202244438
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2022
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 3
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    KMT-2018-BLG-1025Lb: microlensing super-Earth planet orbiting a low-mass star
    EDP Sciences ; 2021
    In:  Astronomy & Astrophysics Vol. 649 ( 2021-5), p. A90-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 649 ( 2021-5), p. A90-
    Abstract: Aims. We aim to find missing microlensing planets hidden in the unanalyzed lensing events of previous survey data. Methods. For this purpose, we conducted a systematic inspection of high-magnification microlensing events, with peak magnifications of A peak ≳ 30, in the data collected from high-cadence surveys in and before the 2018 season. From this investigation, we identified 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. Results. 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 ~ 0.8 × 10 −4 for solution A and q ~ 1.6 × 10 −4 for 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 p , M h , D L ) ~ (6.1  M ⊕ , 0.22  M ⊙ , 6.7 kpc) for solution A and ~(4.4  M ⊕ , 0.08  M ⊙ , 7.5 kpc) for 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, which were discovered by microlensing.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202039817
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2021
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
    Location Call Number Limitation Availability
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  • 4
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    KMT-2018-BLG-0748Lb: sub-Saturn microlensing planet orbiting an ultracool host
    EDP Sciences ; 2020
    In:  Astronomy & Astrophysics Vol. 641 ( 2020-9), p. A105-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 641 ( 2020-9), p. A105-
    Abstract: Aims. We announce the discovery of a microlensing planetary system, in which a sub-Saturn planet is orbiting an ultracool dwarf host. Methods. We detected the planetary system by analyzing the short-timescale ( t E ~ 4.4 days) lensing event KMT-2018-BLG-0748. The central part of the light curve exhibits asymmetry due to negative deviations in the rising side and positive deviations in the falling side. Results. We find that the deviations are explained by a binary-lens model with a mass ratio between the lens components of q ~ 2 × 10 −3 . The short event timescale, together with the small angular Einstein radius, θ E ~ 0.11 mas, indicate that the mass of the planet host is very small. The Bayesian analysis conducted under the assumption that the planet frequency is independent of the host mass indicates that the mass of the planet is M p = 0.18 −0.10 +0.29 M J , and the mass of the host, M h = 0.087 −0.047 +0.138 M ⊙ , is near the star–brown dwarf boundary, but the estimated host mass is sensitive to this assumption about the planet hosting probability. High-resolution follow-up observations would lead to revealing the nature of the planet host.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202038173
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2020
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
    Location Call Number Limitation Availability
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  • 5
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    Four microlensing planets with faint-source stars identified in the 2016 and 2017 season data
    EDP Sciences ; 2020
    In:  Astronomy & Astrophysics Vol. 642 ( 2020-10), p. A110-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 642 ( 2020-10), p. A110-
    Abstract: Aims. Microlensing planets occurring on faint-source stars can escape detection due to their weak signals. Occasionally, detections of such planets are not reported due to the difficulty of extracting high-profile scientific issues on the detected planets. Methods. For the solid demographic census of microlensing planetary systems based on a complete sample, we investigate the microlensing data obtained in the 2016 and 2017 seasons to search for planetary signals in faint-source lensing events. From this investigation, we find four unpublished microlensing planets: KMT-2016-BLG-2364Lb, KMT-2016-BLG-2397Lb, OGLE-2017-BLG-0604Lb, and OGLE-2017-BLG-1375Lb. Results. We analyze the observed lensing light curves and determine their lensing parameters. From Bayesian analyses conducted with the constraints from the measured parameters, it is found that the masses of the hosts and planets are in the ranges 0.50 ≲ M host ∕ M ⊙ ≲ 0.85 and 0.5 ≲ M p ∕ M J ≲ 13.2, respectively, indicating that all planets are giant planets around host stars with subsolar masses. The lenses are located in the distance range of 3.8 ≲ D L ∕kpc ≲ 6.4. It is found that the lenses of OGLE-2017-BLG-0604 and OGLE-2017-BLG-1375 are likely to be in the Galactic disk.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202039066
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2020
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
    Location Call Number Limitation Availability
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  • 6
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    KMT-2021-BLG-0240: Microlensing event with a deformed planetary signal
    EDP Sciences ; 2022
    In:  Astronomy & Astrophysics Vol. 664 ( 2022-8), p. A114-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 664 ( 2022-8), p. A114-
    Abstract: Aims. The light curve of the microlensing event KMT-2021-BLG-0240 exhibits a short-lasting anomaly with complex features near the peak at the 0.1 mag level from a single-lens single-source 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 binary-lens (2L1S) or a binary-source (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 triple-lens (3L1S) model or a binary-lens binary-source (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 sub-Jovian-mass 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 K-dwarf 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.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202243161
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2022
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
    Location Call Number Limitation Availability
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  • 7
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    KMT-2021-BLG-1122L: The first microlensing triple stellar system
    EDP Sciences ; 2023
    In:  Astronomy & Astrophysics Vol. 672 ( 2023-04), p. A8-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 672 ( 2023-04), p. A8-
    Abstract: 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 binary-lens or binary-source interpretations. Methods. 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 events presented in our previous work, here we present the 3L1S analysis of the KMT-2021-BLG-1122. Results. It is found that the lens of the event KMT-2021-BLG-1122 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 KMT-2018-BLG-2119 is the first triple stellar system detected via microlensing.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202245644
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2023
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
    Location Call Number Limitation Availability
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  • 8
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    MOA-2022-BLG-249Lb: Nearby microlensing super-Earth planet detected from high-cadence surveys
    EDP Sciences ; 2023
    In:  Astronomy & Astrophysics Vol. 674 ( 2023-6), p. A89-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 674 ( 2023-6), p. A89-
    Abstract: Aims. We investigate the data collected by the high-cadence 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 MOA-2022-BLG-249 exhibits a brief positive anomaly that lasted for about one day, with a maximum deviation of ~0.2 mag from a single-source, single-lens model. Methods. We analyzed the light curve under the two interpretations of the anomaly: one originated by a low-mass companion to the lens (planetary model) and the other originated by a faint companion to the source (binary-source model). Results. We find that the anomaly is better explained by the planetary model than the binary-source model. We identified two solutions rooted in the inner-outer degeneracy and for both of them, the estimated planet-to-host 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 blend-flux constraint, we find that the lens is a planetary system, in which a super-Earth planet, with a mass of (4.83 ± 1.44) Μ ⊕ , orbits a low-mass 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 high-cadence lensing surveys to low-mass planets.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202346166
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2023
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
    Location Call Number Limitation Availability
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  • 9
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    KMT-2021-BLG-2010Lb, KMT-2022-BLG-0371Lb, and KMT-2022-BLG-1013Lb: Three microlensing planets detected via partially covered signals
    EDP Sciences ; 2023
    In:  Astronomy & Astrophysics Vol. 674 ( 2023-6), p. A90-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 674 ( 2023-6), p. A90-
    Abstract: Aims. We inspect the four microlensing events KMT-2021-BLG-1968, KMT-2021-BLG-2010, KMT-2022-BLG-0371, and KMT-2022-BLG-1013, for which the light curves exhibit partially covered short-term 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 binary-lens (2L1S) and binary-source (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 KMT-2021-BLG-2010 and KMT-2022-BLG-1013 are uniquely defined by planetary-lens interpretations with planet-to-host mass ratios of q ~ 2.8 × 10 −3 and ~1.6 × 10 −3 , respectively. For KMT-2022-BLG-0371, 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 KMT-2021-BLG-1968, on the other hand, we find that the anomaly can be explained either by a planetary or a binary-source 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 KMT-2021-BLG-2010L, KMT-2022-BLG-0371L, and KMT-2022-BLG-1013L, respectively.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202346298
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2023
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
    Location Call Number Limitation Availability
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  • 10
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    KMT-2022-BLG-0475Lb and KMT-2022-BLG-1480Lb: Microlensing ice giants detected via the non-caustic-crossing channel
    EDP Sciences ; 2023
    In:  Astronomy & Astrophysics Vol. 676 ( 2023-8), p. A97-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 676 ( 2023-8), p. A97-
    Abstract: Aims. We investigate the microlensing data collected in the 2022 season from high-cadence microlensing surveys in order to find weak signals produced by planetary companions to lenses. Methods. From these searches, we find that two lensing events, KMT-2022-BLG-0475 and KMT-2022-BLG-1480, exhibit weak short-term anomalies. From a detailed modeling of the lensing light curves, we determine that the anomalies are produced by planetary companions with a mass ratio to the primary of q ~ 1.8 × 10 −4 for KMT-2022-BLG-0475L and q ~ 4.3 × 10 −4 for KMT-2022-BLG-1480L. Results. We estimate that the host and planet masses and the projected planet-host separation are ( M h / M ⊙ , M p / M U , a ⊥ /au) = (0.43 −0.23 +0.35 , 1.73 −0.92 +1.42 , 2.03 −0.38 +0.25 ) for KMT-2022-BLG-0475L and (0.18 −0.09 +0.16 , 1.82 −0.92 +1.60 , 1.22 −0.14 +0.15 ) for KMT-2022-BLG-1480L, where M U denotes the mass of Uranus. The two planetary systems have some characteristics in common: the primaries of the lenses are early-mid M dwarfs that lie in the Galactic bulge, and the companions are ice giants that lie beyond the snow lines of the planetary systems.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202346667
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2023
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
    Location Call Number Limitation Availability
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