Probable brown dwarf companions detected in binary microlensing events during the 2018–2020 seasons of the KMTNet survey

¹ Department of Physics, Chungbuk National University, Cheongju 28644, Republic of Korea
e-mail: cheongho@astroph.chungbuk.ac.kr
² Korea Astronomy and Space Science Institute, Daejon 34055, Republic of Korea
³ Max-Planck-Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
⁴ Department of Astronomy, Ohio State University, 140 W. 18th Ave., Columbus, OH 43210, USA
⁵ Dipartimento di Fisica “E. R. Caianiello”, Universitá di Salerno, Via Giovanni Paolo II, 84084 Fisciano (SA), Italy
⁶ Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Via Cintia, 80126 Napoli, Italy
⁷ Institute of Natural and Mathematical Science, Massey University, Auckland 0745, New Zealand
⁸ University of Canterbury, Department of Physics and Astronomy, Private Bag 4800, Christchurch 8020, New Zealand
⁹ Center for Astrophysics, Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA
¹⁰ Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100, Israel
¹¹ Department of Astronomy, Tsinghua University, Beijing 100084, PR China
¹² School of Space Research, Kyung Hee University, Yongin, Kyeonggi 17104, Republic of Korea
¹³ Korea University of Science and Technology, Korea, (UST), 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea
¹⁴ Institute for Space-Earth Environmental Research, Nagoya University, Nagoya 464-8601, Japan
¹⁵ Code 667, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
¹⁶ Department of Astronomy, University of Maryland, College Park, MD 20742, USA
¹⁷ Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
¹⁸ Instituto de Astrofísica de Canarias, Via Láctea s/n, 38205 La Laguna, Tenerife, Spain
¹⁹ Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
²⁰ Department of Physics, The Catholic University of America, Washington, DC 20064, USA
²¹ Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
²² Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Mönchhofstr. 12–14, 69120 Heidelberg, Germany
²³ Department of Physics, University of Auckland, Private Bag 92019, Auckland, New Zealand
²⁴ University of Canterbury Mt. John Observatory, PO Box 56, Lake Tekapo 8770, New Zealand

Received: 14 November 2022
Accepted: 9 May 2023

Abstract

Aims. We inspect the microlensing data of the KMTNet survey collected during the 2018-2020 seasons in order to find lensing events produced by binaries with brown dwarf (BD) companions.

Methods. In order to pick out binary-lens events with candidate BD lens companions, we conducted systematic analyses of all anomalous lensing events observed during the seasons from 2018 to 2020. By applying a selection criterion of mass ratio between the lens components of 0.03 ≲ q ≲ 0.1, we identify four binary-lens events with candidate BD companions, namely KMT-2018-BLG-0321, KMT-2018-BLG-0885, KMT-2019-BLG-0297, and KMT-2019-BLG-0335. For the individual events, we present interpretations of the lens systems and measure the observables that can be used to constrain the physical lens parameters.

Results. The masses of the lens companions estimated from the Bayesian analyses based on the measured observables indicate high probabilities that the lens companions are in the BD mass regime; that is, 59%, 68%, 66%, and 66% for the four respective events.