Epsilon Indi Ba, Bb: a spectroscopic study of the nearest known brown dwarfs

TL;DR

This study provides detailed spectroscopic and photometric characterization of the nearest known brown dwarf binary system, Epsilon Indi Ba and Bb, offering valuable benchmarks to test and refine atmospheric and evolutionary models of cool substellar objects.

Contribution

It presents comprehensive broadband spectra and photometry of Epsilon Indi Ba and Bb, including a novel spectral analysis and constraints on their physical parameters, aiding model validation.

Findings

Spectral types confirmed as T1 and T6.

No lithium detected in the more massive component.

Spectroscopic data spans 0.6-5.1 microns at R=5000.

Abstract

The discovery of Epsilon Indi Ba and Bb, a nearby binary brown dwarf system with a main-sequence companion, allows a concerted campaign to characterise the physical parameters of two T dwarfs providing benchmarks against which atmospheric and evolutionary models can be tested. Some recent observations suggest the models at low mass and intermediate age may not reflect reality with, however, few conclusive tests. We are carrying out a comprehensive characterisation of these, the nearest known brown dwarfs, to allow constraints to be placed upon models of cool field dwarfs. We present broadband photometry from the V- to M-band and the individual spectrum of both components from 0.6-5.1 microns at a resolution of up to R=5000. A custom analytic profile fitting routine was implemented to extract the blended spectra and photometry of both components separated by 0.7 arcsec. We confirm the spectral types to be T1 and T6, and notably, we do not detect lithium at 6708A in the more massive object which may be indicative both of the age of the system and the mass of the components.