Two Low-Mass-Ratio Microlensing Planets from High-Magnification Events: KMT-2021-BLG-0247 and MOA-2023-BLG-169
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 ML=0.9±0.1 M⊙ and DL=6.7+1.0−0.3 kpc, respectively, and the planet mass is Mp=41±5 M⊕. The projected planet--host separations are a⊥=3.4+0.7−0.3 au and 3.0+0.6−0.3 au for the wide and close solutions, respectively. In contrast, MOA-2023-BLG-169 involves an extremely faint source, with IS,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 VISAB=23.05±0.09 mag. Interpreting this component as the combined light from the source and any luminous lens, the resulting posterior gives ML=0.48+0.23−0.17 M⊙, DL=3.50+2.82−1.20 kpc, a⊥=1.62+0.77−0.43 au, and Mp=143+103−63 M⊕. 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.
Related
- Gaia Science Alerts microlensing events with mass estimates verifiable in Gaia Data Release 4
- An equal mass ratio supermassive binary black holes in Q J0158-4325 with periodic microlensing signature?
- The Galactic Dynamics of Free-Floating Planets: From Ejection Kicks to Microlensing
- lenscape: Fast, High-resolution Δχ2 Maps of Microlensing Events
- Same Events, Weaker Bound: Model Dependence in Magellanic Microlensing Limits on Primordial Black Holes
BibTeX
@misc{nunota2026lowmassratio,
title = {{Two Low-Mass-Ratio Microlensing Planets from High-Magnification Events: KMT-2021-BLG-0247 and MOA-2023-BLG-169}},
author = {Kansuke Nunota and Andrew Gould and Takahiro Sumi and Ian A. Bond and Jennifer C. Yee and Valerio Bozza and Fumio Abe and David P. Bennett and Aparna Bhattacharya and Kotaro Daimon and Ryusei Hamada and Yuki Hirao and Takuto Inoue and Stela Ishitani Silva and Shuma Makida and Shota Miyazaki and Yasushi Muraki and Seiya Nakayama and Ryo Ogawa and Ryunosuke Oishi and Greg Olmschenk and Hideaki Ose and Clément Ranc and Nicholas J. Rattenbury and Yuki K. Satoh and Daisuke Suzuki and Takuto Tamaoki and Sean K. Terry and Paul J. Tristram and Chihiro Ueda and Aikaterini Vandorou and Hibiki Yama and Michael D. Albrow and Sun-Ju Chung and Cheongho Han and Kyu-Ha Hwang and Youn Kil Jung and Yoon-Hyun Ryu and In-Gu Shin and Yossi Shvartzvald and Hongjing Yang and Weicheng Zang and Dong-Jin Kim and Chung-Uk Lee and Byeong-Gon Park and Andrzej Udalski and Przemek Mróz and Radosław Poleski and Jan Skowron and Michał K. Szymański and Igor Soszyński and Paweł Pietrukowicz and Szymon Kozłowski and Krzysztof Ulaczyk and Krzysztof A. Rybicki and Patryk Iwanek and Marcin Wrona and Mariusz Gromadzki and Mateusz J. Mróz},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.10308},
eprint = {2610.10308},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.10308},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Two Low-Mass-Ratio Microlensing Planets from High-Magnification Events: KMT-2021-BLG-0247 and MOA-2023-BLG-169
AU - Kansuke Nunota
AU - Andrew Gould
AU - Takahiro Sumi
AU - Ian A. Bond
AU - Jennifer C. Yee
AU - Valerio Bozza
AU - Fumio Abe
AU - David P. Bennett
AU - Aparna Bhattacharya
AU - Kotaro Daimon
AU - Ryusei Hamada
AU - Yuki Hirao
AU - Takuto Inoue
AU - Stela Ishitani Silva
AU - Shuma Makida
AU - Shota Miyazaki
AU - Yasushi Muraki
AU - Seiya Nakayama
AU - Ryo Ogawa
AU - Ryunosuke Oishi
AU - Greg Olmschenk
AU - Hideaki Ose
AU - Clément Ranc
AU - Nicholas J. Rattenbury
AU - Yuki K. Satoh
AU - Daisuke Suzuki
AU - Takuto Tamaoki
AU - Sean K. Terry
AU - Paul J. Tristram
AU - Chihiro Ueda
AU - Aikaterini Vandorou
AU - Hibiki Yama
AU - Michael D. Albrow
AU - Sun-Ju Chung
AU - Cheongho Han
AU - Kyu-Ha Hwang
AU - Youn Kil Jung
AU - Yoon-Hyun Ryu
AU - In-Gu Shin
AU - Yossi Shvartzvald
AU - Hongjing Yang
AU - Weicheng Zang
AU - Dong-Jin Kim
AU - Chung-Uk Lee
AU - Byeong-Gon Park
AU - Andrzej Udalski
AU - Przemek Mróz
AU - Radosław Poleski
AU - Jan Skowron
AU - Michał K. Szymański
AU - Igor Soszyński
AU - Paweł Pietrukowicz
AU - Szymon Kozłowski
AU - Krzysztof Ulaczyk
AU - Krzysztof A. Rybicki
AU - Patryk Iwanek
AU - Marcin Wrona
AU - Mariusz Gromadzki
AU - Mateusz J. Mróz
PY - 2026
DA - 2026/10/08
PB - arXiv
DO - 10.48550/arxiv.2610.10308
UR - https://arxiv.org/abs/2610.10308
AB - 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_L=0.9±0.1 M_⊙ and D_L=6.7^+1.0_−0.3 kpc, respectively, and the planet mass is M_p=41±5 M_⊕. The projected planet--host separations are a_⊥=3.4^+0.7_−0.3 au and 3.0^+0.6_−0.3 au for the wide and close solutions, respectively. In contrast, MOA-2023-BLG-169 involves an extremely faint source, with I_S,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 VIS_AB=23.05±0.09 mag. Interpreting this component as the combined light from the source and any luminous lens, the resulting posterior gives M_L=0.48^+0.23_−0.17 M_⊙, D_L=3.50^+2.82_−1.20 kpc, a_⊥=1.62^+0.77_−0.43 au, and M_p=143^+103_−63 M_⊕. 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.
ER -