KMT-2021-BLG-0171Lb and KMT-2021-BLG-1689Lb: Two Microlensing Planets in the KMTNet High-cadence Fields with Followup Observations
Creators: name: Yang, Hongjing
name: Zang, Weicheng
name: Gould, Andrew
name: Yee, Jennifer C.
name: Hwang, Kyu-Ha
name: Christie, Grant
name: Sumi, Takahiro
name: Zhang, Jiyuan
name: Mao, Shude
name: Albrow, Michael D.
name: Chung, Sun-Ju
name: Han, Cheongho
name: Jung, Youn Kil
name: Ryu, Yoon-Hyun
name: Shin, In-Gu
name: Shvartzvald, Yossi
name: Cha, Sang-Mok
name: Kim, Dong-Jin
name: Kim, Hyoun-Woo
name: Kim, Seung-Lee
name: Lee, Chung-Uk
name: Lee, Dong-Joo
name: Lee, Yongseok
name: Park, Byeong-Gon
name: Pogge, Richard W.
name: Drummond, John
name: Maoz, Dan
name: McCormick, Jennie
name: Natusch, Tim
name: Penny, Matthew T.
name: Zhu, Wei
name: Bond, Ian A.
name: Abe, Fumio
name: Barry, Richard
name: Bennett, David P.
name: Bhattacharya, Aparna
name: Donachie, Martin
name: Fujii, Hirosane
name: Fukui, Akihiko
name: Hirao, Yuki
name: Itow, Yoshitaka
name: Kirikawa, Rintaro
name: Kondo, Iona
name: Koshimoto, Naoki
name: Li, Man Cheung Alex
name: Matsubara, Yutaka
name: Muraki, Yasushi
name: Miyazaki, Shota
name: Olmschenk, Greg
name: Ranc, Clément
name: Rattenbury, Nicholas J.
name: Satoh, Yuki
name: Shoji, Hikaru
name: Silva, Stela Ishitani
name: Suzuki, Daisuke
name: Tanaka, Yuzuru
name: Tristram, Paul J.
name: Yamawaki, Tsubasa
name: Yonehara, Atsunori
Publisher: name: arXiv
Year: 2022
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: Follow-up observations of high-magnification gravitational microlensing events can fully exploit their intrinsic sensitivity to detect extrasolar planets, especially those with small mass ratios. To make followup more uniform and efficient, we develop a system, HighMagFinder, based on the real-time data from the Korean Microlensing Telescope Network (KMTNet) to automatically alert possible ongoing high-magnification events. We started a new phase of follow-up observations with the help of HighMagFinder in 2021. Here we report the discovery of two planets in high-magnification microlensing events, KMT-2021-BLG-0171 and KMT-2021-BLG-1689, which were identified by the HighMagFinder. We find that both events suffer the ``central-resonant'' caustic degeneracy. The planet-host mass-ratio is $q\sim4.7\times10^{-5}$ or $q\sim 2.2\times10^{-5}$ for KMT-2021-BLG-0171, and $q\sim2.5\times10^{-4}$ or $q\sim 1.8\times10^{-4}$ for KMT-2021-BLG-1689. Together with two events reported by Ryu et al. (2022), four cases that suffer such degeneracy have been discovered in the 2021 season alone, indicating that the degenerate solutions may have been missed in some previous studies. We also propose a new factor for weighting the probability of each solution from the phase-space. The resonant interpretations for the two events are disfavored under this consideration. This factor can be included in future statistical studies to weight degenerate solutions.
description: 18 pages, 15 figures, 10 tabels; submitted to MNRAS