WISEP J061135.13-041024.0AB: A J-Band Flux Reversal Binary at the L/T Transition

TL;DR

This paper reports the discovery and analysis of a binary brown dwarf system exhibiting a flux reversal in the J-band at the L/T transition, providing insights into brown dwarf atmospheres and evolution.

Contribution

It presents high-resolution imaging, spectral deconvolution, and atmospheric modeling of a unique binary brown dwarf system with flux reversal, advancing understanding of L/T transition phenomena.

Findings

Binary system with 0.4" separation and spectral types L9 and T1.5.

System contributes to the J-band bump in brown dwarf evolution.

Estimated age >1 Gyr, with component temperatures around 1075-1325 K.

Abstract

We present Keck II laser guide star adaptive optics observations of the brown dwarf WISEP J061135.13-041024.0 showing it is a binary with a component separation of 0.4". This system is one of the six known resolved binaries in which the magnitude differences between the components show a reversal in sign between the Y/J band and the H/K bands. Deconvolution of the composite spectrum results in a best fit binary solution with L9 and T1.5 components. We also present a preliminary parallax placing the system at a distance of 21.2+/-1.3 pc. Using the distance and resolved magnitudes we are able to place WISEP J061135.13-041024.0AB on a color-absolute magnitude diagram, showing that this system contributes to the well-known "J-band bump" and the components' properties appear similar to other late-type L and early-type T dwarfs. Fitting our data to a set of cloudy atmosphere models suggests the system has an age >1 Gyr with WISEP J061135.13-041024.0A having an effective temperature (Teff) of 1275-1325 K and mass of 64-65 M_Jup, and WISEP J061135.13-041024.0B having Teff = 1075-1115 K and mass 40-65 M_Jup.