KMT-2022-BLG-0440Lb: A new q < 10-4 microlensing planet with the central-resonant caustic degeneracy broken
Maoz, Dan; Han, Cheongho; Lee, Chung-Uk; Zang, Weicheng; Albrow, Michael D.; Chung, Sun-Ju; Gould, Andrew; Hwang, Kyu-Ha; Jung, Youn Kil; Ryu, Yoon-Hyun; Shvartzvald, Yossi; Shin, In-Gu; Yee, Jennifer C.; Yang, Hongjing; Cha, Sang-Mok; Kim, Dong-Jin; Kim, Seung-Lee; Lee, Dong-Joo; Lee, Yongseok; Park, Byeong-Gon; Pogge, Richard W.; Dong, Subo; Fukui, Akihiko; Penny, Matthew T.; Kim, Hyoun-Woo; Zhu, Wei; Sumi, Takahiro; Mao, Shude; Bond, Ian A.; Abe, Fumio; Barry, Richard; Bennett, David P.; Bhattacharya, Aparna; Fujii, Hirosane; Hirao, Yuki; Itow, Yoshitaka; Kirikawa, Rintaro; Kondo, Iona; Koshimoto, Naoki; Matsubara, Yutaka; Muraki, Yasushi; Miyazaki, Shota; Olmschenk, Greg; Ranc, Clément; Rattenbury, Nicholas J.; Satoh, Yuki; Suzuki, Daisuke; Tristram, Paul J.; Silva, Stela Ishitani; Matsumoto, Sho; Okamura, Arisa; Toda, Taiga; Yama, Hibiki; Vandorou, Aikaterini; MOA Collaboration; Hamada, Ryusei; Tomoyoshi, Mio; Yamashita, Kansuke; Zhang, Jiyuan; Liu, Zhuokai; Qian, Qiyue
China, United States, South Korea, Germany, Japan, New Zealand, Israel, Spain, France
Abstract
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 1σ. The binary-lens models with a resonant caustic and a brown-dwarf mass ratio are both excluded by Δχ2 > 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 degeneracy. 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.