Luhman 16AB: A Remarkable, Variable L/T Transition Binary 2 pc from the Sun

TL;DR

This paper studies the nearby Luhman 16AB brown dwarf binary, revealing spectral variability, cloud structure differences, and dynamic properties, enhancing understanding of the L/T transition in substellar objects.

Contribution

It presents the first detection of near-infrared spectral variability and detailed analysis of condensate cloud differences in the Luhman 16AB system.

Findings

Detected near-infrared spectral variability.

Analyzed K I lines showing condensate opacity differences.

Estimated radial and rotational velocities.

Abstract

Luhman (2013) has reported the discovery of a brown dwarf binary system only 2.01+/-0.15 pc from the Sun. The binary is well-resolved with a projected separation of 1.5", and spectroscopic observations have identified the components as late-L and early-T dwarfs. The system exhibits several remarkable traits, including a "flux reversal", where the T dwarf is brighter over 0.9-1.3 micron but fainter at other wavelengths; and significant (~10%) short-period (~4.9 hr) photometric variability with a complex light curve. These observations suggest spatial variations in condensate cloud structure, which is known to evolve substantially across the L dwarf/T dwarf transition. Here we report preliminary results from a multi-site monitoring campaign aimed at probing the spectral and temporal properties of this source. Focusing on our spectroscopic observations, we report the first detections of NIR spectral variability, present detailed analysis of K I lines that confirm differences in condensate opacity between the components; and preliminary determinations of radial and rotational velocities based on high-resolution NIR spectroscopy.