SDSS J080531.84+481233.0: An Unresolved L Dwarf/T Dwarf Binary

TL;DR

This paper identifies SDSS J080531.84+481233.0 as an unresolved binary system consisting of L and T dwarf components, providing insights into brown dwarf evolution and demonstrating a spectral template matching method for binary detection.

Contribution

It presents a new spectral analysis revealing the binary nature of the object, offering a novel approach to identify L/T dwarf binaries without high-resolution imaging.

Findings

Spectral features consistent with an L4.5 and T5 binary

Weak methane absorption at 1.6 micron without at 2.2 micron

Binary nature inferred from spectral template matching

Abstract

SDSS J080531.84+481233.0 is a peculiar L-type dwarf that exhibits unusually blue near-infrared and mid-infrared colors and divergent optical (L4) and near-infrared (L9.5) spectral classifications. These peculiar spectral traits have been variously attributed to condensate cloud effects or subsolar metallicity. Here I present an improved near-infrared spectrum of this source which further demonstrates the presence of weak CH4 absorption at 1.6 micron but no corresponding band at 2.2 micron. It is shown that these features can be collectively reproduced by the combined light spectrum of a binary with L4.5 and T5 components, as deduced by spectral template matching. Thus, SDSS J080531.84+481233.0 appears to be a new low-mass binary straddling the L dwarf/T dwarf transition, an evolutionary phase for brown dwarfs that remains poorly understood by current theoretical models. The case of SDSS J080531.84+481233.0 further illustrates how a select range of L dwarf/T dwarf binaries could be identified and characterized without the need for high angular resolution imaging or radial velocity monitoring, potentially alleviating some of the detection biases and limitations inherent to such techniques.