Two Low-Mass-Ratio Microlensing Planets from High-Magnification Events: KMT-2021-BLG-0247 and MOA-2023-BLG-169
Year: 2026
Type: preprint
Abstract: We present an analysis of two planetary microlensing events, KMT-2021-BLG-0247 and MOA-2023-BLG-169, both of which exhibit high magnifications and low planet--host mass ratios, but with markedly different levels of parameter constraint. For KMT-2021-BLG-0247, the finite-source effect and microlens parallax are both clearly detected, leading to unusually tight constraints on the physical properties of the lens system. The host mass and lens distance are approximately $M_{\rm L}=0.9\pm0.1\,M_\odot$ and $D_{\rm L}=6.7^{+1.0}_{-0.3}\,\mathrm{kpc}$, respectively, and the planet mass is $M_{\rm p}=41\pm5\,M_\oplus$. The projected planet--host separations are $a_\perp=3.4^{+0.7}_{-0.3}\,\mathrm{au}$ and $3.0^{+0.6}_{-0.3}\,\mathrm{au}$ for the wide and close solutions, respectively. In contrast, MOA-2023-BLG-169 involves an extremely faint source, with $I_{S,{\rm OGLE}}=26.73$, such that the light curve permits a broad family of strongly correlated solutions. We therefore construct the physical-parameter likelihood using approximate invariant combinations of the light-curve parameters and supplement it with post-event Euclid/VIS imaging from the Euclid Q2 Galactic Bulge Survey (Beaulieu et al. 2026). The Euclid data reveal a component at the event position with ${\rm VIS}_{\rm AB}=23.05\pm0.09\,{\rm mag}$. Interpreting this component as the combined light from the source and any luminous lens, the resulting posterior gives $M_{\rm L}=0.48^{+0.23}_{-0.17}\,M_\odot$, $D_{\rm L}=3.50^{+2.82}_{-1.20}\,\mathrm{kpc}$, $a_\perp=1.62^{+0.77}_{-0.43}\,\mathrm{au}$, and $M_{\rm p}=143^{+103}_{-63}\,M_\oplus$. MOA-2023-BLG-169 demonstrates that, for an extreme faint-source event, even the event timescale and angular Einstein radius can remain strongly dependent on the Galactic prior and independent flux constraints.
Source: arXiv (Cornell University)
Authors: Nunota, Kansuke, Gould, Andrew, Sumi, Takahiro, Bond, Ian A., Yee, Jennifer C., Bozza, Valerio, Abe, Fumio, Bennett, David P., Bhattacharya, Aparna, Daimon, Kotaro, Hamada, Ryusei, Hirao, Yuki, Inoue, Takuto, Silva, Stela Ishitani, Makida, Shuma, Miyazaki, Shota, Muraki, Yasushi, Nakayama, Seiya, Ogawa, Ryo, Oishi, Ryunosuke, Olmschenk, Greg, Ose, Hideaki, Ranc, Clément, Rattenbury, Nicholas J., Satoh, Yuki K., Suzuki, Daisuke, Tamaoki, Takuto, Terry, Sean K., Tristram, Paul J., Ueda, Chihiro, Vandorou, Aikaterini, Yama, Hibiki, Albrow, Michael D., Chung, Sun-Ju, Han, Cheongho, Hwang, Kyu-Ha, Jung, Youn Kil, Ryu, Yoon-Hyun, Shin, In-Gu, Shvartzvald, Yossi, Yang, Hongjing, Zang, Weicheng, Kim, Dong-Jin, Lee, Chung-Uk, Park, Byeong-Gon, Udalski, Andrzej, Mróz, Przemek, Poleski, Radosław, Skowron, Jan, Szymański, Michał K., Soszyński, Igor, Pietrukowicz, Paweł, Kozłowski, Szymon, Ulaczyk, Krzysztof, Rybicki, Krzysztof A., Iwanek, Patryk, Wrona, Marcin, Gromadzki, Mariusz, Mróz, Mateusz J.
Institutions: The University of Osaka, The Ohio State University, Massey University, Center for Astrophysics Harvard & Smithsonian, University of Salerno, Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Institute for Space-Earth Environmental Research, Nagoya University, Nagoya University, Goddard Space Flight Center, University of Maryland, College Park, Institute of Astronomy, Graduate School of Science, The University of Tokyo, The University of Tokyo, Catholic University of America, Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science, Centre National de la Recherche Scientifique, Institut d'Astrophysique de Paris, Sorbonne Université, University of Auckland, Nippon Institute of Technology, University of Canterbury, Kyoto University, Korea Astronomy and Space Science Institute, Chungbuk National University, Korea University of Science and Technology, Westlake University, Weizmann Institute of Science, Tsinghua University, University of Warsaw, University of Warwick, Villanova University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7221039993