Analyses of anomalous lensing events detected from the UKIRT microlensing survey

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 M 1 = (1.05 ± 0.20) M ⊙ , M 2 = (0.36 ± 0.07) M ⊙ , and the distance to the lens was found to be D L = (3.11 ± 0.40) kpc.

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Journal
Astronomy and Astrophysics
Published
2025-03-20
DOI
https://doi.org/10.1051/0004-6361/202553811
Citations
1
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Astronomy and Astrophysical Research
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article
Field-Weighted Citation Impact
1.19
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Analyses of anomalous lensing events detected from the UKIRT microlensing survey

Sang-Mok Cha, Yongseok Lee, I. Soszyński, Michael D. Albrow et al.
1 citations
Astronomy and Astrophysics
Astronomy and Astrophysical Research
1.19
article

Analyses of anomalous lensing events detected from the UKIRT microlensing survey

Sang-Mok Cha, Yongseok Lee, I. Soszyński, Michael D. Albrow, Weicheng Zang, Hongjing Yang, Yuki Satoh, Sean K. Terry, Daisuke Suzuki, Yongxin Wen, M. Gromadzki, Kyu‐Ha Hwang, Akihiko Fukui, Hibiki Yama, ‪Clément Ranc, Naoto Hamasaki, Krzysztof A. Rybicki, D. P. Bennett, M. K. Szymański, J. Skowron, R. Poleski, Yoon-Hyun Ryu, Yossi Shvartzvald, Seung‐Lee Kim, Chung‐Uk Lee, Aparna Bhattacharya, Naoki Koshimoto, Sun‐Ju Chung, Cheongho Han, Aikaterini Vandorou, A. Udalski, Youn Kil Jung, Patryk Iwanek, Shota Miyazaki, Stela Ishitani Silva, I. A. Bond, P. Pietrukowicz, P. Mróz, K. Ulaczyk, Nicholas J. Rattenbury, In-Gu Shin, Greg Olmschenk, Yuki Hirao, Jennifer C. Yee, Y. Matsubara, P. J. Tristram, S. Kozłowski, Richard W. Pogge, Ryusei Hamada, Marcin Wrona, Y. Muraki, Kansuke Nunota, Dong-Jin Kim, Takahiro Sumi, Bo Ma, Tutumi Nagai, Byeong-Gon Park, Dong-Joo Lee, Fumio Abe, Mateusz J. Mroz, Shunya Hamada, Andrew Gould, Doeon Kim, Ken Bando
article en
1 citations

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 M 1 = (1.05 ± 0.20) M ⊙ , M 2 = (0.36 ± 0.07) M ⊙ , and the distance to the lens was found to be D L = (3.11 ± 0.40) kpc.

Astronomy and AstrophysicsVol. 696
Oak Ridge Associated Universities (US), Centre National de la Recherche Scientifique (FR), Goddard Space Flight Center (US), University of Auckland (NZ), Sun Yat-sen University (CN), Chungbuk National University (KR), University of Canterbury (NZ), Korea Astronomy and Space Science Institute (KR), Japan Aerospace Exploration Agency (JP), Institut d'Astrophysique de Paris (FR), Kyung Hee University (KR), University of Warwick (GB), Sorbonne Université (FR), Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (CN), Center for Astrophysics Harvard & Smithsonian (US), Instituto de Astrofísica de Canarias (ES), Institute of Space and Astronautical Science (JP), University of Warsaw (PL), Massey University (NZ), The Ohio State University (US), Weizmann Institute of Science (IL), Nagoya University (JP), University of Maryland, College Park (US), The University of Tokyo (JP), Villanova University (US), The University of Osaka (JP), Tsinghua University (CN)
Openalex Percentile: Top 23%
Astronomy and Astrophysical Research
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