We analyze the binary microlensing event MOA-2016-BLG-231, which was observed from the ground and from Spitzer. The lens is composed of very low-mass brown dwarfs (BDs) with M1=21−5+12MJ and M2=9−2+5MJ, and it is located in the Galactic disk DL=2.85−0.50+0.88kpc. This is the fifth binary brown dwarf discovered by microlensing, and the BD binary is moving counter to the orbital motion of disk stars. Constraints on the lens physical properties come from late time, non-caustic-crossing features of the Spitzer light curve. Thus, MOA-2016-BLG-231 shows how Spitzer plays a crucial role in resolving the nature of BDs in binary BD events with short timescale (≲10 days).
@article{arxiv.1902.03150,
title = {Spitzer Microlensing of MOA-2016-BLG-231L : A Counter-Rotating Brown Dwarf Binary in the Galactic Disk},
author = {Sun-Ju Chung and Andrew Gould and Jan Skowron and Ian A. Bond and Wei Zhu and Michael D. Albrow and Youn Kil Jung and Cheongho Han and Kyu-Ha Hwang and Yoon-Hyun Ryu and In-Gu Shin and Yossi Shvartzvald and Jennifer C. Yee and Weicheng Zang and Sang-Mok Cha and Dong-Jin Kim and Hyoun-Woo Kim and Seung-Lee Kim and Yun-Hak Kim and Chung-Uk Lee and Dong-Joo Lee and Yongseok Lee and Byeong-Gon Park and Richard W. Pogge and Andrzej Udalski and Radek Poleski and Przemek Mróz and Paweł Pietrukowicz and Michał K. Szymański and Igor Soszyński and Szymon Kozłowski and Krzysztof Ulaczyk and Michał Pawlak and Charles A. Beichman and Geoffery Bryden and Sebastiano Calchi Novati and Sean Carey and B. Scott Gaudi and Calen B. Henderson and Fumio Abe and Richard Barry and David P. Bennett and Aparna Bhattacharya and Martin Donachie and Akihiko Fukui and Yuki Hirao and Yoshitaka Itow and Kohei Kawasaki and Iona Kondo and Naoki Koshimoto and Man Cheung Alex Li and Yutaka Matsubara and Yasushi Muraki and Shota Miyazaki and Masayuki Nagakane and Clément Ranc and Nicholas J. Rattenbury and Haruno Suematsu and Denis J. Sullivan and Takahiro Sumi and Daisuke Suzuki and Paul J. Tristram and Atsunori Yonehara},
journal= {arXiv preprint arXiv:1902.03150},
year = {2019}
}