The Astronomical Journal
Jung, Youn Kil; Udalski, Andrzej; Zang, Weicheng; Bond, Ian A.; Yee, Jennifer C.; Han, Cheongho; Albrow, Michael D.; Chung, Sun-Ju; Gould, Andrew; Hwang, Kyu-Ha; Ryu, Yoon-Hyun; Shin, In-Gu; Shvartzvald, Yossi; 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.; KMTNet Collaboration; Mróz, Przemek; Szymański, Michał K.; Skowron, Jan; Poleski, Radek; Soszyński, Igor; Pietrukowicz, Paweł; Kozłowski, Szymon; Ulaczyk, Krzysztof; Rybicki, Krzysztof A.; Iwanek, Patryk; Wrona, Marcin; OGLE Collaboration; Abe, Fumio; Barry, Richard; Bennett, David P.; Bhattacharya, Aparna; Donachie, Martin; Fujii, Hirosame; Fukui, Akihiko; Hirao, Yuki; Itow, Yoshitaka; Kamei, Yukei; Kondo, Iona; Koshimoto, Naoki; Li, Man Cheung Alex; Matsubara, Yutaka; Miyazaki, Shota; Muraki, Yasushi; Nagakane, Masayuki; Ranc, Clément; Rattenbury, Nicholas J.; Satoh, Yuki; Shoji, Hikaru; Suematsu, Haruno; Sullivan, Denis J.; Sumi, Takahiro; Suzuki, Daisuke; Tristram, Paul J.; Yamakawa, Takeharu; Yamamwaki, Tsubasa; Yonehara, Atsunori; MOA Collaboration
We report the discovery of a cold planet with a very low planet/host mass ratio of q = (4.09 ± 0.27) × 10-5, which is similar to the ratio of Uranus/Sun (q = 4.37 × 10-5) in the solar system. The Bayesian estimates for the host mass, planet mass, system distance, and planet-host projected separation are Mhost = 0.76 ± 0.40M☉, Mplanet = 10.3 ± 5.5M⊕, DL = 3.3 ± 1.3 kpc, and a⊥ = 3.3 ± 1.4 au, respectively. The consistency of the color and brightness expected from the estimated lens mass and distance with those of the blend suggests the possibility that the most blended light comes from the planet host, and this hypothesis can be established if high-resolution images are taken during the next (2020) bulge season. We discuss the importance of conducting optimized photometry and aggressive follow-up observations for moderately or very high magnification events to maximize the detection rate of planets with very low mass ratios.