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Precision measurement of a brown dwarf mass in a binary system in the microlensing event

2022; EDP Sciences; Volume: 663; Linguagem: Inglês

10.1051/0004-6361/202243490

1432-0746

A. Herald, A. Udalski, V. Bozza, P. Rota, I. A. Bond, Jennifer C. Yee, Sedighe Sajadian, P. Mróz, R. Poleski, J. Skowron, M. K. Szymański, I. Soszyński, P. Pietrukowicz, S. Kozłowski, K. Ulaczyk, K. Rybicki, Patryk Iwanek, Marcin Wrona, M. Gromadzki, F. Abe, R. Barry, D. P. Bennett, A. Bhattacharya, Akihiko Fukui, Hirosane Fujii, Yuki Hirao, Y. Itow, R. Kirikawa, Iona Kondo, Naoki Koshimoto, Y. Matsubara, Siena Matsumoto, Satoshi Miyazaki, Y. Muraki, Greg Olmschenk, ‪Clément Ranc, A. Okamura, Nicholas J. Rattenbury, Yuki Satoh, T. Sumi, D. Suzuki, S. Ishitani Silva, Taiga Toda, P. J. Tristram, A. Vandorou, H. Yama, C. A. Beichman, G. Bryden, S. Calchi Novati, S. Carey, B. S. Gaudi, A. Gould, Calen B. Henderson, Susan Johnson, Yossi Shvartzvald, Wei Zhu, M. Dominik, M. Hundertmark, Ulrik Jørgensen, Penélope Longa-Peña, J. Skottfelt, J. Tregloan-Reed, Nanna Bach-Møller, M. Burgdorf, G. D’Ago, L. K. Haikala, J. A. Hitchcock, E. Khalouei, N. Peixinho, S. Rahvar, C. Snodgrass, J. Southworth, Petros Spyratos, W. Zang, Hongjing Yang, Shude Mao, E. Bachelet, D. Maoz, R. A. Street, Y. Tsapras, G. W. Christie, Tony Cooper, Leandro de Almeida, J. D. do Nascimento, J. Green, Cheongho Han, S. Hennerley, Andrew Marmont, J. McCormick, L. A. G. Monard, T. Natusch, Richard W. Pogge,

Astronomy and Astrophysical Research

Context. Brown dwarfs are poorly understood transition objects between stars and planets, with several competing mechanisms having been proposed for their formation. Mass measurements are generally difficult for isolated objects but also for brown dwarfs orbiting low-mass stars, which are often too faint for spectroscopic follow-up. Aims. Microlensing provides an alternative tool for the discovery and investigation of such faint systems. Here we present the analysis of the microlensing event OGLE-2019-BLG-0033/MOA-2019-BLG-035, which is due to a binary system composed of a brown dwarf orbiting a red dwarf. Methods. Thanks to extensive ground observations and the availability of space observations from Spitzer, it has been possible to obtain accurate estimates of all microlensing parameters, including parallax, source radius and orbital motion of the binary lens. Results. After accurate modeling, we find that the lens is composed of a red dwarf with mass $M_1 = 0.149 \pm 0.010M_\odot$ and a brown dwarf with mass $M_2 = 0.0463 \pm 0.0031M_\odot$, at a projected separation of $a_\perp = 0.585$ au. The system has a peculiar velocity that is typical of old metal-poor populations in the thick disk. Percent precision in the mass measurement of brown dwarfs has been achieved only in a few microlensing events up to now, but will likely become common with the Roman space telescope.