An Earth-mass planet in a time of COVID-19: KMT-2020-BLG-0414Lb

• Published in: Research in astronomy and astrophysics Vol. 21; no. 9; pp. 239 - 261
• Main Authors: Zang, Weicheng, Han, Cheongho, Kondo, Iona, Yee, Jennifer C., Lee, Chung-Uk, Gould, Andrew, Mao, Shude, de Almeida, Leandro, Shvartzvald, Yossi, Zhang, Xiangyu, Albrow, Michael D., Chung, Sun-Ju, Hwang, Kyu-Ha, Jung, Youn Kil, Ryu, Yoon-Hyun, Shin, In-Gu, Cha, Sang-Mok, Kim, Dong-Jin, Kim, Hyoun-Woo, Kim, Seung-Lee, Lee, Dong-Joo, Lee, Yongseok, Park, Byeong-Gon, Pogge, Richard W., Drummond, John, Tan, Thiam-Guan, Nascimento Júnior, José Dias do, Maoz, Dan, Penny, Matthew T., Zhu, Wei, Bond, Ian A., Abe, Fumio, Barry, Richard, Bennett, David P., Bhattacharya, Aparna, Donachie, Martin, Fujii, Hirosane, Fukui, Akihiko, Hirao, Yuki, Itow, Yoshitaka, Kirikawa, Rintaro, Koshimoto, Naoki, Alex Li, Man Cheung, Matsubara, Yutaka, Muraki, Yasushi, Miyazaki, Shota, Olmschenk, Greg, Ranc, Clément, Rattenbury, Nicholas J., Satoh, Yuki, Shoji, Hikaru, Silva, Stela Ishitani, Sumi, Takahiro, Suzuki, Daisuke, Tanaka, Yuzuru, Tristram, Paul J., Yamawaki, Tsubasa, Yonehara, Atsunori, Petric, Andreea, Burdullis, Todd, Fouqué, Pascal
• Format: Journal Article
• Language: English
• Published: Beijing National Astronomical Observatories, CAS and IOP Publishing Ltd 01.11.2021; IOP Publishing; The LCOGT & μFUN Follow-up Teams%Korea Astronomy and Space Science Institute,Daejon 34055,Republic of Korea; The MOA Collaboration%Institute of Space and Astronautical Science,Japan Aerospace Exploration Agency,3-1-1 Yoshinodai,Chuo,Sagamihara,Kanagawa,252-5210,Japan; National Astronomical Observatories,Chinese Academy of Sciences,Beijing 100101,China; The LCOGT & μFUN Follow-up Teams%Universidade Federal do Rio Grande do Norte (UFRN),Departamento de Física,59078-970,Natal,RN,Brazil; CFHT Microlensing Collaboration%Department of Astronomy,Tsinghua University,Beijing 100084,China; Department of Astronomy,Tsinghua University,Beijing 100084,China; The LCOGT & μFUN Follow-up Teams; Department of Astronomy,Ohio State University,140 W.18th Ave.,Columbus,OH 43210,USA; The LCOGT & μFUN Follow-up Teams%Department of Particle Physics and Astrophysics,Weizmann Institute of Science,Rehovot 76100,Israel; The MOA Collaboration%Center for Astrophysics | Harvard & Smithsonian,60 Garden St.,Cambridge,MA 02138,USA; Center for Astrophysics | Harvard & Smithsonian,60 Garden St.,Cambridge,MA 02138,USA; Canadian Institute for Theoretical Astrophysics,University of Toronto,60 St George Street,Toronto,ON M5S 3H8,Canada; The MOA Collaboration%Department of Astronomy,Graduate School of Science,The University of Tokyo,7-3-1 Hongo,Bunkyo-ku,Tokyo 113-0033,Japan; The MOA Collaboration%Department of Physics,The Catholic University of America,Washington,DC 20064,USA; The MOA Collaboration%Code 667,NASA Goddard Space Flight Center,Greenbelt,MD 20771,USA; The MOA Collaboration%CFHT Corporation,65-1238 Mamalahoa Hwy,Kamuela,Hawaii 96743,USA; The LCOGT & μFUN Follow-up Teams%School of Physics and Astronomy,Tel-Aviv University,Tel-Aviv 6997801,Israel; The MOA Collaboration%Department of Physics,University of Auckland,Private Bag 92019,Auckland,New Zealand; National Astronomical Observatory of Japan,2-21-1 Osawa,Mitaka,Tokyo 181-8588,Japan; The KMTNet Collaboration%Max-Planck-Institute for Astronomy,K(o)nigstuhl 17,69117 Heidelberg,Germany; The MOA Collaboration%University of Canterbury Mt.John Observatory,P.O.Box 56,Lake Tekapo 8770,New Zealand; Université de Toulouse,UPS-OMP,IRAP,Toulouse,France; The KMTNet Collaboration%Department of Astronomy,Ohio State University,140 W.18th Ave.,Columbus,OH 43210,USA; The LCOGT & μFUN Follow-up Teams%Department of Physics and Astronomy,Louisiana State University,Baton Rouge,LA 70803 USA; Instituto de Astrofísica de Canarias,Vía Láctea s/n,E-38205 La Laguna,Tenerife,Spain; The KMTNet Collaboration%Department of Earth and Space Science,Graduate School of Science,Osaka University,Toyonaka,Osaka 560-0043,Japan; The MOA Collaboration%Department of Earth and Planetary Science,Graduate School of Science,The University of Tokyo,7-3-1 Hongo,Bunkyo-ku,Tokyo 113-0033,Japan; CFHT Microlensing Collaboration%CFHT Corporation,65-1238 Mamalahoa Hwy,Kamuela,Hawaii 96743,USA; The LCOGT & μFUN Follow-up Teams%Perth Exoplanet Survey Telescope,Perth,Australia; The KMTNet Collaboration; CFHT Microlensing Collaboration%Institute of Natural and Mathematical Sciences,Massey University,Auckland 0745,New Zealand; The KMTNet Collaboration%Korea Astronomy and Space Science Institute,Daejon 34055,Republic of Korea; Code 667,NASA Goddard Space Flight Center,Greenbelt,MD 20771,USA; CFHT Microlensing Collaboration; The MOA Collaboration%Department of Physics,Faculty of Science,Kyoto Sangyo University,603-8555 Kyoto,Japan; The LCOGT & μFUN Follow-up Teams%Department of Astronomy,Tsinghua University,Beijing 100084,China; CFHT Microlensing Collaboration%Department of Physics,Chungbuk National University,Cheongju 28644,Republic of Korea; University of Science and Technology,Korea,(UST),217 Gajeong-ro Yuseong-gu,Daejeon 34113,Republic of Korea; The KMTNet Collaboration%Possum Observatory,Patutahi,Gisbourne,New Zealand; The MOA Collaboration%Institute for Space-Earth Environmental Research,Nagoya University,Nagoya 464-8601,Japan; Space Telescope Science Institute,Baltimore,MD 21211; School of Space Research,Kyung Hee University,Yongin,Kyeonggi 17104,Republic of Korea; Department of Astronomy,University of Maryland,College Park,MD 20742,USA; The LCOGT & μFUN Follow-up Teams%Department of Astronomy,Tsinghua University,Beijing 100084,China%University of Canterbury,Department of Physics and Astronomy,Private Bag 4800,Christchurch 8020,New Zealand; CFHT Microlensing Collaboration%Universidade Federal do Rio Grande do Norte (UFRN),Departamento de Física,59078-970,Natal,RN,Brazil
• Subjects: Coronaviruses; COVID-19; Extrasolar planets; gravitational lensing: micro; Light curve; Microlenses; Parallax; Planets; Sciences of the Universe; Shutdowns; Spectroscopic observation; gravitational lensing:micro; gravitational lensing: micro; Astrophysics - Astrophysics of Galaxies; Astrophysics - High Energy Astrophysical Phenomena; Astrophysics - Earth and Planetary Astrophysics
• DOI: 10.1088/1674-4527/21/9/239
• ISSN: 1674-4527

We report the discovery of KMT-2020-BLG-0414Lb, with a planet-to-host mass ratio q 2 = 0.9–1.2 × 10−5 = 3–4 ⊕ at 1σ, which is the lowest mass-ratio microlensing planet to date. Together with two other recent discoveries (4 ≲ q/q ⊕ ≲ 6), it fills out the previous empty sector at the bottom of the triangular (log s, log q) diagram, where s is the planet-host separation in units of the angular Einstein radius θE. Hence, these discoveries call into question the existence, or at least the strength, of the break in the mass-ratio function that was previously suggested to account for the paucity of very low-q planets. Due to the extreme magnification of the event, A max ∼ 1450 for the underlying single-lens event, its light curve revealed a second companion with q 3 ∼ 0.05 and |log s 3| ∼ 1, i.e., a factor ∼ 10 closer to or farther from the host in projection. The measurements of the microlens parallax π E and the angular Einstein radius θE allow estimates of the host, planet and second companion masses, (M 1, M 2, M 3) ∼ (0.3 M ⊙, 1.0 M ⊕, 17 MJ ), the planet and second companion projected separations, (a ⊥,2, a ⊥,3) ∼ (1.5, 0.15 or 15) au, and system distance D L ∼ 1 kpc. The lens could account for most or all of the blended light (I ∼ 19.3) and so can be studied immediately with high-resolution photometric and spectroscopic observations that can further clarify the nature of the system. The planet was found as part of a new program of high-cadence follow-up observations of high-magnification events. The detection of this planet, despite the considerable difficulties imposed by COVID-19 (two KMT sites and OGLE were shut down), illustrates the potential utility of this program.