The Astrophysical Journal | 2019
Spitzer Microlensing of MOA-2016-BLG-231L: A Counter-rotating Brown Dwarf Binary in the Galactic Disk
Abstract
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 = + M M 21 J 1 5 12 and = + M M 9 J 2 2 5 , and it is located in the Galactic disk = + D 2.85 kpc L 0.50 0.88 . 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, The Astrophysical Journal, 871:179 (13pp), 2019 February 1 https://doi.org/10.3847/1538-4357/aaf861 © 2019. The American Astronomical Society. All rights reserved.