_version_ 1866917327918858240
author Tang, Yuchen
Zang, Weicheng
Ryu, Yoon-Hyun
Udalski, Andrzej
Yang, Hongjing
Albrow, Michael D.
Chung, Sun-Ju
Gould, Andrew
Han, Cheongho
Hwang, Kyu-Ha
Jung, Youn Kil
Shin, In-Gu
Shvartzvald, Yossi
Yee, Jennifer C.
Kim, Dong-Jin
Lee, Chung-Uk
Park, Byeong-Gon
de Almeida, Leandro
Tang, Yunyi
Li, Zhixing
Zhang, Jiyuan
Li, Hongyu
Mao, Shude
Qian, Qiyue
Maoz, Dan
Borges, Christian Elias
Kalaki, Fabrício Santos
Júnior, Altair Ramos Gomes
Zhu, Wei
Mróz, Przemek
Szymański, Michał K.
Skowron, Jan
Poleski, Radosław
Soszyński, Igor
Pietrukowicz, Paweł
Kozłowski, Szymon
Rybicki, Krzysztof A.
Iwanek, Patryk
Ulaczyk, Krzysztof
Wrona, Marcin
Gromadzki, Mariusz
Mróz, Mateusz J.
author_facet Tang, Yuchen
Zang, Weicheng
Ryu, Yoon-Hyun
Udalski, Andrzej
Yang, Hongjing
Albrow, Michael D.
Chung, Sun-Ju
Gould, Andrew
Han, Cheongho
Hwang, Kyu-Ha
Jung, Youn Kil
Shin, In-Gu
Shvartzvald, Yossi
Yee, Jennifer C.
Kim, Dong-Jin
Lee, Chung-Uk
Park, Byeong-Gon
de Almeida, Leandro
Tang, Yunyi
Li, Zhixing
Zhang, Jiyuan
Li, Hongyu
Mao, Shude
Qian, Qiyue
Maoz, Dan
Borges, Christian Elias
Kalaki, Fabrício Santos
Júnior, Altair Ramos Gomes
Zhu, Wei
Mróz, Przemek
Szymański, Michał K.
Skowron, Jan
Poleski, Radosław
Soszyński, Igor
Pietrukowicz, Paweł
Kozłowski, Szymon
Rybicki, Krzysztof A.
Iwanek, Patryk
Ulaczyk, Krzysztof
Wrona, Marcin
Gromadzki, Mariusz
Mróz, Mateusz J.
contents We present observations and analysis of two low planet/host mass-ratio ($q$) microlensing planets discovered in high-magnification events. KMT-2025-BLG-0811Lb has $q \sim 4.5 \times 10^{-5}$, and a Bayesian analysis favors a super-Earth/mini-Neptune orbiting an M- or K-dwarf host at a projected separation of $\sim 3$ au. KMT-2025-BLG-0912Lb has $q = 2.6 \times 10^{-4}$ and likely hosts a super-Earth/mini-Neptune around either a low-mass M dwarf or a brown dwarf at $\sim 1$ au. Even with an observing cadence of $Γ> 30~{\rm hr}^{-1}$ during the planetary signal, KMT-2025-BLG-0811 still exhibits the "central-resonant" degeneracy. Reviewing nine such events, we find that the "central-resonant" degeneracy can be divided into two distinct types that occupy separate regions in the plane of $q$ and normalized source radius ($ρ$). Type~I events have similar $q$ but substantially different $ρ$ and are more difficult to resolve from the light curves. For Type~II events, the "resonant" solutions have relatively lower $q$ and larger $ρ$. Our review provides guidance for searching for the alternative solution once one solution has been identified.
format Preprint
id arxiv_https___arxiv_org_abs_2603_09045
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Two Low Mass-Ratio Microlensing Planets and Two Types of Central-Resonant Degeneracy
Tang, Yuchen
Zang, Weicheng
Ryu, Yoon-Hyun
Udalski, Andrzej
Yang, Hongjing
Albrow, Michael D.
Chung, Sun-Ju
Gould, Andrew
Han, Cheongho
Hwang, Kyu-Ha
Jung, Youn Kil
Shin, In-Gu
Shvartzvald, Yossi
Yee, Jennifer C.
Kim, Dong-Jin
Lee, Chung-Uk
Park, Byeong-Gon
de Almeida, Leandro
Tang, Yunyi
Li, Zhixing
Zhang, Jiyuan
Li, Hongyu
Mao, Shude
Qian, Qiyue
Maoz, Dan
Borges, Christian Elias
Kalaki, Fabrício Santos
Júnior, Altair Ramos Gomes
Zhu, Wei
Mróz, Przemek
Szymański, Michał K.
Skowron, Jan
Poleski, Radosław
Soszyński, Igor
Pietrukowicz, Paweł
Kozłowski, Szymon
Rybicki, Krzysztof A.
Iwanek, Patryk
Ulaczyk, Krzysztof
Wrona, Marcin
Gromadzki, Mariusz
Mróz, Mateusz J.
Earth and Planetary Astrophysics
We present observations and analysis of two low planet/host mass-ratio ($q$) microlensing planets discovered in high-magnification events. KMT-2025-BLG-0811Lb has $q \sim 4.5 \times 10^{-5}$, and a Bayesian analysis favors a super-Earth/mini-Neptune orbiting an M- or K-dwarf host at a projected separation of $\sim 3$ au. KMT-2025-BLG-0912Lb has $q = 2.6 \times 10^{-4}$ and likely hosts a super-Earth/mini-Neptune around either a low-mass M dwarf or a brown dwarf at $\sim 1$ au. Even with an observing cadence of $Γ> 30~{\rm hr}^{-1}$ during the planetary signal, KMT-2025-BLG-0811 still exhibits the "central-resonant" degeneracy. Reviewing nine such events, we find that the "central-resonant" degeneracy can be divided into two distinct types that occupy separate regions in the plane of $q$ and normalized source radius ($ρ$). Type~I events have similar $q$ but substantially different $ρ$ and are more difficult to resolve from the light curves. For Type~II events, the "resonant" solutions have relatively lower $q$ and larger $ρ$. Our review provides guidance for searching for the alternative solution once one solution has been identified.
title Two Low Mass-Ratio Microlensing Planets and Two Types of Central-Resonant Degeneracy
topic Earth and Planetary Astrophysics
url https://arxiv.org/abs/2603.09045