We report on the analysis of high-resolution infrared spectra of the newly discovered brown dwarf \epsilon Indi B .
This is the closest known brown dwarf to the solar system , with a distance of 3.626 pc .
Spectra covering the ranges of \lambda 2.308–2.317 \mu m and \lambda 1.553–1.559 \mu m were observed at a resolution of \lambda / \Delta \lambda =R=50,000 .
The physical parameters of effective temperature and surface gravity are derived for \epsilon Ind Ba by comparison with model spectra calculated from atmospheres computed using unified cloudy models .
The results are T _ { eff } = 1500 \pm 100K , log g= 5.2 \pm 0.3 ( in units of cm s ^ { -2 } ) , placing it in the critical boundary between the late-L and early-T dwarfs .
The high spectral resolution also allows us to measure an accurate projected rotational velocity , with vsin ( \iota ) = 28 \pm 3 km s ^ { -1 } .
Combined with a published luminosity for \epsilon Ind Ba ( with log ( L/L _ { \odot } ) = -4.67 ) , the derived parameters result in a “ spectroscopic ” mass estimate of \sim 32M _ { Jupiter } , a radius of \sim 0.07R _ { \odot } , and a maximum rotational period of \sim 3.0 hours .
A compilation and comparison of effective temperatures derived from spectroscopy using model atmospheres versus those derived from luminosities and theoretical M _ { bol } –radius relations reveals a systematic disagreement in the T _ { eff } scale .
The source of this disagreement is unknown .