Kmt-2022-Blg-0440lb: A New q < 10−4 Microlensing Planet With the Central-Resonant Caustic Degeneracy Broken

• Published in: Monthly notices of the Royal Astronomical Society Vol. 522; no. 4; pp. 6055 - 6069
• Main Authors: Zhang, Jiyuan, Zang, Weicheng, Jung, Youn Kil, Yang, Hongjing, Gould, Andrew, Sumi, Takahiro, Mao, Shude, Dong, Subo, Albrow, Michael D, Chung, Sun-Ju, Han, Cheongho, Hwang, Kyu-Ha, Ryu, Yoon-Hyun, Shin, In-Gu, Shvartzvald, Yossi, Yee, Jennifer C, Cha, Sang-Mok, Kim, Dong-Jin, Kim, Hyoun-Woo, Kim, Seung-Lee, Lee, Chung-Uk, Lee, Dong-Joo, Lee, Yongseok, Park, Byeong-Gon, Pogge, Richard W, Qian, Qiyue, Liu, Zhuokai, Maoz, Dan, Penny, Matthew T, Zhu, Wei, Abe, Fumio, Barry, Richard, Bennett, David P, Bhattacharya, Aparna, Bond, Ian A, Silva, Stela Ishitani, Koshimoto, Naoki, Olmschenk, Greg, Vandorou, Aikaterini
• Format: Journal Article
• Language: English
• Published: Goddard Space Flight Center Oxford University Press (United Kingdom) 11.05.2023; Oxford University Press
• Subjects: Astronomy; Gravitational Lensing: Micro; Planets And Satellites: Detection; gravitational lensing: micro; planets and satellites: detection
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stad1398

We present the observations and analysis of a high-magnification microlensing planetary event, KMT-2022-BLG-0440, for which the weak and short-lived planetary signal was covered by both the KMTNet survey and follow-up observations. The binary-lens models with a central caustic provide the best fits, with a planet/host mass ratio, q = 0.75–1.00 ×10−4 at 1 σ. The binary-lens models with a resonant caustic and a brown-dwarf mass ratio are both excluded by ∆χ2 > 70. The binary-source model can fit the anomaly well but is rejected by the ‘colour argument’ on the second source. From Bayesian analyses, it is estimated that the host star is likely a K or M dwarf located in the Galactic disc, the planet probably has a Neptune-mass, and the projected planet-host separation is 1.9+0.6−0.7 or 4.6+1.4−1.7 au, subject to the close/wide de generac y. This is the third q < 10−4 planet from a high-magnification planetary signal ( A ≳ 65). Together with another such planet, KMT-2021-BLG-0171Lb, the ongoing follow-up program for the KMTNet high-magnification events has demonstrated its ability to detect high-magnification planetary signals for q < 10−4 planets, which are challenging for the current microlensing surveys.