CWISE J014611.20–050850.0AB: The Widest Known Brown Dwarf Binary in the Field

While stars are often found in binary systems, brown dwarf binaries much rarer. Brown dwarf--brown pairs typically difficult to resolve because they have very small separations. Using dwarfs discovered with data from the Wide-field Infrared Survey Explorer (WISE) via Backyard Worlds: Planet 9 citizen science project, we inspected other, higher resolution, sky surveys for overlooked cold companions. During this process system CWISE J0146$-$0508AB, which find has a chance alignment probability based on similar proper motions of components system. follow-up near-infrared spectroscopy Keck/NIRES, determined component spectral types L4 and L8 (blue), making J0146$-$0508AB one only few benchmark systems blue L dwarf. At an estimated distance $\sim$40 pc, projected separation $\sim$129 AU, it widest pair date. We that such wide may imply formation low-density star-forming region.