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  • Physics  (26)
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  • 1
    Online Resource
    Online Resource
    KMT-2021-BLG-1150Lb: Microlensing planet detected through a densely covered planetary-caustic signal
    EDP Sciences ; 2023
    In:  Astronomy & Astrophysics Vol. 675 ( 2023-7), p. A36-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 675 ( 2023-7), p. A36-
    Abstract: Aims. Recently, there have been reports of various types of degeneracies in the interpretation of planetary signals induced by planetary caustics. In this work we check whether such degeneracies persist in the case of well-covered signals by analyzing the lensing event KMT-2021-BLG-1150, the light curve of which exhibits a densely and continuously covered short-term anomaly. Methods. In order to identify degenerate solutions, we thoroughly investigated the parameter space by conducting dense grid searches for the lensing parameters. We then checked the severity of the degeneracy among the identified solutions. Results. We identify a pair of planetary solutions resulting from the well-known inner-outer degeneracy, and find that interpreting the anomaly is not subject to any degeneracy other than the inner-outer degeneracy. The measured parameters of the planet separation (normalized to the Einstein radius) and mass ratio between the lens components are ( s , q ) in ~ (1.297, 1.10 × 10 −3 ) for the inner solution and ( s , q ) out ~ (1.242, 1.15 × 10 −3 ) for the outer solution. According to a Bayesian estimation, the lens is a planetary system consisting of a planet with a mass M p = 0.88 −0.36 +0.38 M j and its host with a mass M h = 0.73 −0.30 +0.32 M ⊙ lying toward the Galactic center at a distance D L = 3.8 −1.2 +1.3 kpc. By conducting analyses using mock data sets prepared to mimic those obtained with data gaps and under various observational cadences, we find that gaps in data can result in various degenerate solutions, while the observational cadence does not pose a serious degeneracy problem as long as the anomaly feature can be delineated.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202346596
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2023
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 2
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    KMT-2021-BLG-1898: Planetary microlensing event involved with binary source stars
    EDP Sciences ; 2022
    In:  Astronomy & Astrophysics Vol. 663 ( 2022-7), p. A145-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 663 ( 2022-7), p. A145-
    Abstract: Aims. 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. 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 double-bump feature of the anomaly can also be depicted by a triple-lens 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, KMT-2021-BLG-1898 is the third planetary lensing event occurring on a binary stellar system, following MOA-2010-BLG-117 and KMT-2018-BLG-1743. Results. Under the 2L2S interpretation, we identify two solutions resulting from the close-wide degeneracy in determining the planet-host 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 planet-host separation is ~1.9 AU and ~3.0 AU according to the close and wide solutions, respectively.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202243102
    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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    Two new free-floating or wide-orbit planets from microlensing
    EDP Sciences ; 2019
    In:  Astronomy & Astrophysics Vol. 622 ( 2019-2), p. A201-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 622 ( 2019-2), p. A201-
    Abstract: Planet formation theories predict the existence of free-floating planets that have been ejected from their parent systems. Although they emit little or no light, they can be detected during gravitational microlensing events. Microlensing events caused by rogue planets are characterized by very short timescales t E (typically below two days) and small angular Einstein radii θ E (up to several μ as). Here we present the discovery and characterization of two ultra-short microlensing events identified in data from the Optical Gravitational Lensing Experiment (OGLE) survey, which may have been caused by free-floating or wide-orbit planets. OGLE-2012-BLG-1323 is one of the shortest events discovered thus far ( t E = 0.155 ± 0.005 d, θ E = 2.37 ± 0.10 μ as) and was caused by an Earth-mass object in the Galactic disk or a Neptune-mass planet in the Galactic bulge. OGLE-2017-BLG-0560 ( t E = 0.905 ± 0.005 d, θ E = 38.7 ± 1.6 μ as) was caused by a Jupiter-mass planet in the Galactic disk or a brown dwarf in the bulge. We rule out stellar companions up to a distance of 6.0 and 3.9 au, respectively. We suggest that the lensing objects, whether located on very wide orbits or free-floating, may originate from the same physical mechanism. Although the sample of ultrashort microlensing events is small, these detections are consistent with low-mass wide-orbit or unbound planets being more common than stars in the Milky Way.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/201834557
    RVK:
    UA 1000
    RVK:
    US 1090
    Language: English
    Publisher: EDP Sciences
    Publication Date: 2019
    detail.hit.zdb_id: 1458466-9
    SSG: 16,12
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  • 4
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    KMT-2018-BLG-1743: planetary microlensing event occurring on two source stars
    EDP Sciences ; 2021
    In:  Astronomy & Astrophysics Vol. 652 ( 2021-8), p. A145-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 652 ( 2021-8), p. A145-
    Abstract: Aims. We present the analysis of the microlensing event KMT-2018-BLG-1743. The analysis was conducted as a part of the project, in which previous lensing events detected in and before the 2019 season by the KMTNet survey were reinvestigated with the aim of finding solutions of anomalous events with no suggested plausible models. Methods. The light curve of the event, with a peak magnification A peak ~ 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 with Δ χ 2 ~ 188 and ~91 over the 2L1S and 3L1S solutions, respectively. Assuming that these Δ χ 2 values are adequate for distinguishing the models, the event is the fourth 2L2S event and the second 2L2S planetary event. The 2L2S interpretations are subject to a degeneracy, resulting in two solutions with s 〉 1.0 (wide solution) and s 〈 1.0 (close solution). Results. The masses of the lens components and the distance to the lens are ( M host / M ⊙ , M planet / M J , D L /kpc)~(0.19 −0.111 +0.27 ,0.25 −0.14 +0.34 ,6.48 −1.03 +0.94 ) and ~(0.42 −0.25 +0.34 ,1.61 −0.97 +1.30 ,6.04 −1.27 +0.93 ) according to the wide and close solutions, respectively. The source is a binary composed of an early G dwarf and a mid M dwarf. The values of the relative lens-source proper motion expected from the two degenerate solutions, μ wide ~ 2.3 mas yr −1 and μ close ~ 4.1 mas yr −1 , are substantially different, and thus the degeneracy can be broken by resolving the lens and source from future high-resolution imaging observations.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202140923
    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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  • 5
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    Three faint-source microlensing planets detected via the resonant-caustic channel
    EDP Sciences ; 2021
    In:  Astronomy & Astrophysics Vol. 655 ( 2021-11), p. A21-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 655 ( 2021-11), p. A21-
    Abstract: Aims. We conducted a project of reinvestigating the 2017–2019 microlensing data collected by high-cadence surveys with the aim of finding planets that were missed due to the deviations of planetary signals from the typical form of short-term anomalies. Methods. The project led us to find three planets, KMT-2017-BLG-2509Lb, OGLE-2017-BLG-1099Lb, and OGLE-2019-BLG-0299Lb. The lensing light curves of the events have a common characteristic: the planetary signals were produced by the crossings of faint source stars over the resonant caustics formed by giant planets located near the Einstein rings of host stars. Results. For all planetary events, the lensing solutions are uniquely determined without any degeneracy. It is estimated that the host masses are in the range of 0.45 ≲ M ∕ M ⊙ ≲ 0.59, which corresponds to early M to late K dwarfs, and thus the host stars are less massive than the Sun. On the other hand, the planets, with masses in the range of 2.1 ≲ M ∕ M J ≲ 6.2, are heavier than the heaviest planet of the Solar System, that is, Jupiter. The planets in all systems lie beyond the snow lines of the hosts, and thus the discovered planetary systems, together with many other microlensing planetary systems, support the idea that massive gas-giant planets are commonplace around low-mass stars. We discuss the role of late-time high-resolution imaging in clarifying resonant-image lenses with very faint sources.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202141517
    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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  • 6
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    KMT-2019-BLG-0797: Binary-lensing event occurring on a binary stellar system
    EDP Sciences ; 2021
    In:  Astronomy & Astrophysics Vol. 649 ( 2021-05), p. A91-
    Details
    In: Astronomy & Astrophysics, EDP Sciences, Vol. 649 ( 2021-05), p. A91-
    Abstract: Aims. We analyze the microlensing event KMT-2019-BLG-0797. The light curve of the event exhibits two anomalous features from a single-lens single-source model, and we aim to reveal the nature of the anomaly. Methods. It is found that a model with two lenses plus a single source (2L1S model) can explain one feature of the anomaly, but the other feature cannot be explained. We test various models and find that both anomalous features can be explained by introducing an extra source to a 2L1S model (2L2S model), making the event the third confirmed case of a 2L2S event, following MOA-2010-BLG-117 and OGLE-2016-BLG-1003. It is estimated that the extra source comprises ∼4% of the I -band flux from the primary source. Results. Interpreting the event is subject to a close–wide degeneracy. According to the close solution, the lens is a binary consisting of two brown dwarfs with masses ( M 1 ,  M 2 ) ∼ (0.034, 0.021)  M ⊙ , and it is located at a distance of D L  ∼ 8.2 kpc. According to the wide solution, on the other hand, the lens is composed of an object at the star–brown dwarf boundary and an M dwarf with masses ( M 1 ,  M 2 ) ∼ (0.06, 0.33)  M ⊙ located at D L  ∼ 7.7 kpc. The source is composed of a late G dwarf to early K dwarf primary and an early-to-mid M dwarf companion.
    Type of Medium: Online Resource
    ISSN: 0004-6361 , 1432-0746
    URL: Article
    DOI: 10.1051/0004-6361/202040149
    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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  • 7
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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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  • 8
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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
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  • 9
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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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  • 10
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    Online Resource
    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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