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

TL;DR

This paper reports the discovery of the widest known brown dwarf binary system in the field, using infrared survey data and follow-up spectroscopy, providing insights into brown dwarf formation and binary characteristics.

Contribution

The study presents the identification and characterization of CWISE J0146$-$0508AB, the widest known brown dwarf binary, with detailed spectral analysis and implications for formation environments.

Findings

Discovered the widest brown dwarf binary at ~129 AU separation.

Spectral types of L4 and L8 for the components, including a blue L dwarf.

Suggests formation in a low-density star-forming region.

Abstract

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