Brown dwarf companions in microlensing binaries detected during the 2016–2018 seasons

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 Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka Osaka, 560-0043, Japan
⁴ Dipartimento di Fisica “E. R. Caianiello”, Universitá di Salerno, Via Giovanni Paolo II, 84084 Fisciano SA, Italy
⁵ Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Via Cintia, 80126 Napoli, Italy
⁶ University of Canterbury, Department of Physics and Astronomy, Private Bag 4800 Christchurch, 8020, New Zealand
⁷ Department of Astronomy, Tsinghua University, Beijing 100084, PR China
⁸ Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
⁹ Institute of Natural and Mathematical Science, Massey University, Auckland 0745, New Zealand
¹⁰ Max-Planck-Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
¹¹ Department of Astronomy, Ohio State University, 140 W. 18th Ave., Columbus, OH 43210, USA
¹² Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100, Israel
¹³ School of Space Research, Kyung Hee University, Yongin, Kyeonggi 17104, Republic of Korea
¹⁴ Korea University of Science and Technology, Korea, (UST), 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea
¹⁵ Center for Astrophysics, Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA
¹⁶ Department of Physics, University of Warwick, Gibbet Hill Road Coventry, CV4 7AL, UK
¹⁷ Institute for Space-Earth Environmental Research, Nagoya University, Nagoya 464-8601, Japan
¹⁸ Code 667, NASA Goddard Space Flight Center, Greenbelt MD, 20771, USA
¹⁹ Department of Astronomy, University of Maryland, College Park MD, 20742, USA
²⁰ Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
²¹ Instituto de Astrofísica de Canarias, Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
²² Department of Physics, The Catholic University of America, Washington, DC 20064, USA
²³ Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
²⁴ Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Mönchhofstr. 12-14, 69120 Heidelberg, Germany
²⁵ Department of Physics, University of Auckland, Private Bag 92019, Auckland, New Zealand
²⁶ University of Canterbury Mt. John Observatory, PO Box 56, Lake Tekapo 8770, New Zealand

Received: 4 June 2022
Accepted: 8 September 2022

Abstract

Aims. With the aim of finding microlensing binaries containing brown dwarf (BD) companions, we investigate the microlensing survey data collected during the 2016–2018 seasons.

Methods. For this purpose, we first modeled lensing events with light curves exhibiting anomaly features that are likely to be produced by binary lenses. We then sorted out BD companion binary-lens events by applying the criterion that the companion-to-primary mass ratio is q ≲ 0.1. With this procedure, we identify six binaries with candidate BD companions: OGLE-2016-BLG-0890L, MOA-2017-BLG-477L, OGLE-2017-BLG-0614L, KMT-2018-BLG-0357L, OGLE-2018-BLG-1489L, and OGLE-2018-BLG-0360L.

Results. We estimated the masses of the binary companions by conducting Bayesian analyses using the observables of the individual lensing events. According to the Bayesian estimation of the lens masses, the probabilities for the lens companions of the events OGLE-2016-BLG-0890, OGLE-2017-BLG-0614, OGLE-2018-BLG-1489, and OGLE-2018-BLG-0360 to be in the BD mass regime are very high with P_BD > 80%. For MOA-2017-BLG-477 and KMT-2018-BLG-0357, the probabilities are relatively low with P_BD = 61% and 69%, respectively.