Microlensing brown-dwarf companions in binaries detected during the 2022 and 2023 seasons

¹ Department of Physics, Chungbuk National University, Cheongju 28644, Republic of Korea
² Institute of Natural and Mathematical Science, Massey University, Auckland 0745, New Zealand
³ Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
⁴ Korea Astronomy and Space Science Institute, Daejon 34055, Republic of Korea
⁵ Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany
⁶ Department of Astronomy, The Ohio State University, 140 W. 18th Ave., Columbus, OH 43210, USA
⁷ University of Canterbury, Department of Physics and Astronomy, Private Bag 4800, Christchurch 8020, New Zealand
⁸ Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100, Israel
⁹ Center for Astrophysics | Harvard & Smithsonian 60 Garden St., Cambridge, MA 02138, USA
¹⁰ Department of Astronomy and Tsinghua Centre for Astrophysics, Tsinghua University, Beijing 100084, China
¹¹ School of Space Research, Kyung Hee University, Yongin, Kyeonggi 17104, Republic of Korea
¹² Institute for Space-Earth Environmental Research, Nagoya University, Nagoya 464-8601, Japan
¹³ Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
¹⁴ Code 667, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
¹⁵ Department of Astronomy, University of Maryland, College Park, MD 20742, USA
¹⁶ Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
¹⁷ Instituto de Astrofísica de Canarias, Vía Láctea s/n, E-38205 La Laguna, Tenerife, Spain
¹⁸ Institute of Astronomy, Graduate School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan
¹⁹ Oak Ridge Associated Universities, Oak Ridge, TN 37830, USA
²⁰ Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara, Kanagawa 252-5210, Japan
²¹ Sorbonne Université, CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98 bis bd Arago, 75014 Paris, France
²² Department of Physics, University of Auckland, Private Bag 92019, Auckland, New Zealand
²³ University of Canterbury Mt. John Observatory, P.O. Box 56 Lake Tekapo 8770, New Zealand
²⁴ Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
²⁵ Villanova University, Department of Astrophysics and Planetary Sciences, 800 Lancaster Ave., Villanova, PA 19085, USA

^⋆ Corresponding author; leecu@kasi.re.kr

Received: 7 July 2024
Accepted: 18 August 2024

Abstract

Aims. Building on previous works to construct a homogeneous sample of brown dwarfs in binary systems, we investigate microlensing events detected by the Korea Microlensing Telescope Network (KMTNet) survey during the 2022 and 2023 seasons.

Methods. Given the difficulty in distinguishing brown-dwarf events from those produced by binary lenses with nearly equal-mass components, we analyze all lensing events detected during the seasons that exhibit anomalies characteristic of binary-lens systems.

Results. Using the same criteria consistently applied in previous studies, we identify six additional brown dwarf candidates through the analysis of lensing events KMT-2022-BLG-0412, KMT-2022-BLG-2286, KMT-2023-BLG-0201, KMT-2023-BLG-0601, KMT-2023-BLG-1684, and KMT-2023-BLG-1743. An examination of the mass posteriors shows that the median mass of the lens companions ranges from 0.02 M_⊙ to 0.05 M_⊙, indicating that these companions fall within the brown-dwarf mass range. The mass of the primary lenses ranges from 0.11 M_⊙ to 0.68 M_⊙, indicating that they are low-mass stars with substantially lower masses compared to the Sun.