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arXiv · 2508.11079

Four binary microlenses with directly measured masses

Cheongho Han·Andrzej Udalski·Chung-Uk Lee·Ian A. Bond·Michael D. Albrow·Sun-Ju Chung·Andrew Gould·Youn Kil Jung·Kyu-Ha Hwang·Yoon-Hyun Ryu·Yossi Shvartzvald·In-Gu Shin·Jennifer C. Yee·Weicheng Zang·Hongjing Yang·Sang-Mok Cha·Doeon Kim·Dong-Jin Kim·Seung-Lee Kim·Dong-Joo Lee·Yongseok Lee·Byeong-Gon Park·Richard W. Pogge·Przemek Mróz·Michał K. Szymański·Jan Skowron·Radosław Poleski·Igor Soszyński·Paweł Pietrukowicz·Szymon Kozłowski·Krzysztof A. Rybicki·Patryk Iwanek·Krzysztof Ulaczyk·Marcin Wrona·Mariusz Gromadzki·Mateusz J. Mróz·Michał Jaroszyński·Marcin Kiraga·Fumio Abe·David P. Bennett·Aparna Bhattacharya·Akihiko Fukui·Ryusei Hamada·Stela Ishitani Silva·Yuki Hirao·Naoki Koshimoto·Yutaka Matsubara·Shota Miyazaki·Yasushi Muraki·Tutumi Nagai·Kansuke Nunota·Greg Olmschenk·Clément Ranc·Nicholas J. Rattenbury·Yuki Satoh·Takahiro Sumi·Daisuke Suzuki·Sean K. Terry·Paul J. Tristram·Aikaterini Vandorou·Hibiki Yama
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Abstract

We investigated binary lens events from the 2022-2024 microlensing surveys, aiming to identify events suitable for lens mass measurements. We focused on two key light curve features: distinct caustic spikes with resolved crossings for measuring the angular Einstein radius ($\theta_{\rm E}$), and long durations enabling microlens-parallax ($\pi_{\rm E}$) measurements. Four events met these criteria: KMT-2022-BLG-1479, KMT-2023-BLG-0932, OGLE-2024-BLG-0142, and KMT-2024-BLG-1309. We estimated the angular Einstein radius by combining the normalized source radius measured from modeling the resolved caustic spikes with the angular source radius derived from the source color and magnitude. Additionally, we determined the microlens parallax through light curve modeling, considering higher-order effects caused by the orbital motions of Earth and the binary lens. With measurements of the event timescale, angular Einstein radius, and microlens parallax, we uniquely determined the mass and distance of the lens. For the events KMT-2022-BLG-1479, KMT-2023-BLG-0932, and KMT-2024-BLG-1309, both components of the binary lens have masses lower than that of the Sun, consistent with M-type dwarfs, which are the most common type of lenses in Galactic microlensing events. These lenses are relatively nearby, with distances $\lesssim 2.5$ kpc, indicating their location within the Galactic disk. In contrast, for OGLE-2024-BLG-0142, the primary lens component has a mass similar to that of the Sun, while the companion lens component has about half the mass of the primary. This lens system is situated at a greater distance, roughly 4.5 kpc.

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Cheongho Han, Andrzej Udalski, Chung-Uk Lee, Ian A. Bond, Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Youn Kil Jung, Kyu-Ha Hwang, Yoon-Hyun Ryu, Yossi Shvartzvald, In-Gu Shin, Jennifer C. Yee, Weicheng Zang, Hongjing Yang, Sang-Mok Cha, Doeon Kim, Dong-Jin Kim, Seung-Lee Kim, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, Przemek Mróz, Michał K. Szymański, Jan Skowron, Radosław Poleski, Igor Soszyński, Paweł Pietrukowicz, Szymon Kozłowski, Krzysztof A. Rybicki, Patryk Iwanek, Krzysztof Ulaczyk, Marcin Wrona, Mariusz Gromadzki, Mateusz J. Mróz, Michał Jaroszyński, Marcin Kiraga, Fumio Abe, David P. Bennett, Aparna Bhattacharya, Akihiko Fukui, Ryusei Hamada, Stela Ishitani Silva, Yuki Hirao, Naoki Koshimoto, Yutaka Matsubara, Shota Miyazaki, Yasushi Muraki, Tutumi Nagai, Kansuke Nunota, Greg Olmschenk, Clément Ranc, Nicholas J. Rattenbury, Yuki Satoh, Takahiro Sumi, Daisuke Suzuki, Sean K. Terry, Paul J. Tristram, Aikaterini Vandorou, Hibiki Yama. 2025-08-14. Four binary microlenses with directly measured masses. https://arxiv.org/abs/2508.11079

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