Analyses of anomalous lensing events detected from the UKIRT microlensing survey

MOA Collaboration

doi:10.1051/0004-6361/202553811

Analyses of anomalous lensing events detected from the UKIRT microlensing survey

, MOA Collaboration

Department of Particle Physics and Astrophysics

Research output: Contribution to journal › Article › peer-review

Abstract

Aims. The United Kingdom Infrared Telescope (UKIRT) microlensing survey was conducted over four years, from 2016 to 2019, with the goal of serving as a precursor to future near-infrared microlensing surveys. Focusing on stars in the Galactic center and utilizing near-infrared passbands, the survey identified approximately one thousand microlensing events, 27 of which displayed anomalies in their light curves. This paper presents an analysis of these anomalous events, aiming to uncover the underlying causes of the observed anomalies. Methods. The events were analyzed under various configurations, considering the potential binarity of both the lens and the source. For 11 events that were additionally observed by other optical microlensing surveys, including those conducted by the OGLE, KMTNet, and MOA collaborations, we incorporated their data into our analysis. Results. Among the reported anomalous events, we revealed the nature of 24 events except for three events, in which one was likely to be a transient variable, and two were difficult to accurately characterize their nature due to the limitations of the available data. We confirmed the binary lens nature of the anomalies in 22 events. Among these, we verified the earlier discovery that the companion in the binary lens system UKIRT11L is a planetary object. Accurately describing the anomaly in UKIRT21 required a model that accounted for the binarity of both the lens and the source. For two events UKIRT01 and UKIRT17, the anomalies could be interpreted using either a binary-source or a binary-lens model. For the UKIRT05, it was found that accounting for higher-order effects induced by the orbit al motions of both Earth and the binary lens was crucial. With the measured microlensing parallax togeter with the angular Einstein radius, the component masses of the UKIRT05 binary lens were determined to be M₁ = (1.05 ± 0.20) M_⊙, M₂ = (0.36 ± 0.07) M_⊙, and the distance to the lens was found to be D_L = (3.11 ± 0.40) kpc.

Original language	English
Article number	A126
Journal	Astronomy and Astrophysics
Volume	696
DOIs	https://doi.org/10.1051/0004-6361/202553811
Publication status	Published - 1 Apr 2025

Funding

This research was supported by the Korea Astronomy and Space Science Institute under the R&D program (Project No. 2025-1-830-05) supervised by the Ministry of Science and ICT. This research has made use of the KMTNet system operated by the Korea Astronomy and Space Science Institute (KASI) at three host sites of CTIO in Chile, SAAO in South Africa, and SSO in Australia. Data transfer from the host site to KASI was supported by the Korea Research Environment Open NETwork (KREONET). This research was supported by the KASI under the R&D program (Project No. 2023-1-832-03) supervised by the Ministry of Science and ICT. The MOA project is supported by JSPS KAKENHI Grant Number JP24253004, JP26247023,JP16H06287 and JP22H00153. J.C.Y., I.G.S., and S.J.C. acknowledge support from NSF Grant No. AST-2108414. C.R. was supported by the Research fellowship of the Alexander von Humboldt Foundation. W. Zang and H.Y. acknowledge support by the National Natural Science Foundation of China (Grant No. 12133005). W. Zang acknowledges the support from the Harvard-Smithsonian Center for Astrophysics through the CfA Fellowship.

All Science Journal Classification (ASJC) codes

Astronomy and Astrophysics
Space and Planetary Science

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Cite this

@article{be17449280864e9a91e9dfcf3909f42c,

title = "Analyses of anomalous lensing events detected from the UKIRT microlensing survey",

abstract = "Aims. The United Kingdom Infrared Telescope (UKIRT) microlensing survey was conducted over four years, from 2016 to 2019, with the goal of serving as a precursor to future near-infrared microlensing surveys. Focusing on stars in the Galactic center and utilizing near-infrared passbands, the survey identified approximately one thousand microlensing events, 27 of which displayed anomalies in their light curves. This paper presents an analysis of these anomalous events, aiming to uncover the underlying causes of the observed anomalies. Methods. The events were analyzed under various configurations, considering the potential binarity of both the lens and the source. For 11 events that were additionally observed by other optical microlensing surveys, including those conducted by the OGLE, KMTNet, and MOA collaborations, we incorporated their data into our analysis. Results. Among the reported anomalous events, we revealed the nature of 24 events except for three events, in which one was likely to be a transient variable, and two were difficult to accurately characterize their nature due to the limitations of the available data. We confirmed the binary lens nature of the anomalies in 22 events. Among these, we verified the earlier discovery that the companion in the binary lens system UKIRT11L is a planetary object. Accurately describing the anomaly in UKIRT21 required a model that accounted for the binarity of both the lens and the source. For two events UKIRT01 and UKIRT17, the anomalies could be interpreted using either a binary-source or a binary-lens model. For the UKIRT05, it was found that accounting for higher-order effects induced by the orbit al motions of both Earth and the binary lens was crucial. With the measured microlensing parallax togeter with the angular Einstein radius, the component masses of the UKIRT05 binary lens were determined to be M1 = (1.05 ± 0.20) M⊙, M2 = (0.36 ± 0.07) M⊙, and the distance to the lens was found to be DL = (3.11 ± 0.40) kpc.",

author = "\{MOA Collaboration\} and Cheongho Han and Weicheng Zang and Andrzej Udalski and Lee, \{Chung Uk\} and Bond, \{Ian A.\} and Yongxin Wen and Bo Ma and Albrow, \{Michael D.\} and Chung, \{Sun Ju\} and Andrew Gould and Hwang, \{Kyu Ha\} and Jung, \{Youn Kil\} and Ryu, \{Yoon Hyun\} and Yossi Shvartzvald and Shin, \{In Gu\} and Hongjing Yang and Yee, \{Jennifer C.\} and Doeon Kim and Kim, \{Dong Jin\} and Rybicki, \{Krzysztof A.\}",

year = "2025",

month = apr,

day = "1",

doi = "10.1051/0004-6361/202553811",

language = "English",

volume = "696",

journal = "Astronomy and Astrophysics",

issn = "0004-6361",

publisher = "EDP Sciences",

}

TY - JOUR

T1 - Analyses of anomalous lensing events detected from the UKIRT microlensing survey

AU - MOA Collaboration

AU - Han, Cheongho

AU - Zang, Weicheng

AU - Udalski, Andrzej

AU - Lee, Chung Uk

AU - Bond, Ian A.

AU - Wen, Yongxin

AU - Ma, Bo

AU - Albrow, Michael D.

AU - Chung, Sun Ju

AU - Gould, Andrew

AU - Hwang, Kyu Ha

AU - Jung, Youn Kil

AU - Ryu, Yoon Hyun

AU - Shvartzvald, Yossi

AU - Shin, In Gu

AU - Yang, Hongjing

AU - Yee, Jennifer C.

AU - Kim, Doeon

AU - Kim, Dong Jin

AU - Rybicki, Krzysztof A.

PY - 2025/4/1

Y1 - 2025/4/1

N2 - Aims. The United Kingdom Infrared Telescope (UKIRT) microlensing survey was conducted over four years, from 2016 to 2019, with the goal of serving as a precursor to future near-infrared microlensing surveys. Focusing on stars in the Galactic center and utilizing near-infrared passbands, the survey identified approximately one thousand microlensing events, 27 of which displayed anomalies in their light curves. This paper presents an analysis of these anomalous events, aiming to uncover the underlying causes of the observed anomalies. Methods. The events were analyzed under various configurations, considering the potential binarity of both the lens and the source. For 11 events that were additionally observed by other optical microlensing surveys, including those conducted by the OGLE, KMTNet, and MOA collaborations, we incorporated their data into our analysis. Results. Among the reported anomalous events, we revealed the nature of 24 events except for three events, in which one was likely to be a transient variable, and two were difficult to accurately characterize their nature due to the limitations of the available data. We confirmed the binary lens nature of the anomalies in 22 events. Among these, we verified the earlier discovery that the companion in the binary lens system UKIRT11L is a planetary object. Accurately describing the anomaly in UKIRT21 required a model that accounted for the binarity of both the lens and the source. For two events UKIRT01 and UKIRT17, the anomalies could be interpreted using either a binary-source or a binary-lens model. For the UKIRT05, it was found that accounting for higher-order effects induced by the orbit al motions of both Earth and the binary lens was crucial. With the measured microlensing parallax togeter with the angular Einstein radius, the component masses of the UKIRT05 binary lens were determined to be M1 = (1.05 ± 0.20) M⊙, M2 = (0.36 ± 0.07) M⊙, and the distance to the lens was found to be DL = (3.11 ± 0.40) kpc.

AB - Aims. The United Kingdom Infrared Telescope (UKIRT) microlensing survey was conducted over four years, from 2016 to 2019, with the goal of serving as a precursor to future near-infrared microlensing surveys. Focusing on stars in the Galactic center and utilizing near-infrared passbands, the survey identified approximately one thousand microlensing events, 27 of which displayed anomalies in their light curves. This paper presents an analysis of these anomalous events, aiming to uncover the underlying causes of the observed anomalies. Methods. The events were analyzed under various configurations, considering the potential binarity of both the lens and the source. For 11 events that were additionally observed by other optical microlensing surveys, including those conducted by the OGLE, KMTNet, and MOA collaborations, we incorporated their data into our analysis. Results. Among the reported anomalous events, we revealed the nature of 24 events except for three events, in which one was likely to be a transient variable, and two were difficult to accurately characterize their nature due to the limitations of the available data. We confirmed the binary lens nature of the anomalies in 22 events. Among these, we verified the earlier discovery that the companion in the binary lens system UKIRT11L is a planetary object. Accurately describing the anomaly in UKIRT21 required a model that accounted for the binarity of both the lens and the source. For two events UKIRT01 and UKIRT17, the anomalies could be interpreted using either a binary-source or a binary-lens model. For the UKIRT05, it was found that accounting for higher-order effects induced by the orbit al motions of both Earth and the binary lens was crucial. With the measured microlensing parallax togeter with the angular Einstein radius, the component masses of the UKIRT05 binary lens were determined to be M1 = (1.05 ± 0.20) M⊙, M2 = (0.36 ± 0.07) M⊙, and the distance to the lens was found to be DL = (3.11 ± 0.40) kpc.

UR - https://www.scopus.com/pages/publications/105003034844

U2 - 10.1051/0004-6361/202553811

DO - 10.1051/0004-6361/202553811

M3 - Article

AN - SCOPUS:105003034844

SN - 0004-6361

VL - 696

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

M1 - A126

ER -

Analyses of anomalous lensing events detected from the UKIRT microlensing survey

Abstract

Funding

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