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  • 1
    In: The Astronomical Journal, American Astronomical Society, Vol. 159, No. 3 ( 2020-02-11), p. 98-
    Type of Medium: Online Resource
    ISSN: 1538-3881
    Language: Unknown
    Publisher: American Astronomical Society
    Publication Date: 2020
    detail.hit.zdb_id: 2207625-6
    detail.hit.zdb_id: 2003104-X
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  • 2
    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
    RVK:
    RVK:
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2021
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 3
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 662 ( 2022-6), p. A70-
    Abstract: Aims. 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. Methods. We test various models in combination with several interpretations: that the lens is a binary (2L1S), the source is a binary (1L2S), both the lens and source are binaries (2L2S), or the lens is a triple system (3L1S). We search for the best-fit models under the individual interpretations of the lens and source systems. Results. 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 features in the lensing light curve. According to the 3L1S interpretation, the estimated mass ratios of the lens companions to the primary are ~1.56 × 10 −3 and ~1.75 × 10 −3 , which correspond to ~1.6 and ~1.8 times the Jupiter/Sun mass ratio, respectively, and therefore the lens is a multiplanetary system containing two giant planets. With the constraints of the event time-scale and angular Einstein radius, it is found that the host of the lens system is a low-mass star of mid-to-late M spectral type with amass of M h = 0.14 −0.07 +0.19 M Θ , and it hosts two gas giant planets with masses of M p1 = 0.22 −0.12 +0.31 M J and M p2 = 0.25 −0.13 +0.35 . The planets lie beyond the snow line of the host with projected separations of a ⊥,p1 = 1.26 −1.08 +1.41 AU and a ⊥,p2 = 0.93 −0.80 +1.05 AU. The planetary system resides in the Galactic bulge at a distance of D L = 8.24 −1.16 +1.02 kpc. The lens of the event is the fifth confirmed multiplanetary system detected by microlensing following OGLE-2006-BLG-109L, OGLE-2012-BLG-0026L, OGLE-2018-BLG-1011L, and OGLE-2019-BLG-0468L.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    RVK:
    RVK:
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2022
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 4
    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
    RVK:
    RVK:
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2022
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 5
    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
    RVK:
    RVK:
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2021
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 6
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 658 ( 2022-2), p. A62-
    Abstract: 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, M planet  = 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 M host  = 0.47 −0.25 +0.33  M ⊙ and a distance of D L  = 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.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    RVK:
    RVK:
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2022
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 7
    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
    RVK:
    RVK:
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2020
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 8
    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
    RVK:
    RVK:
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2020
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 9
    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
    RVK:
    RVK:
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2022
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 10
    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
    RVK:
    RVK:
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2023
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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