  Recent wide-field near-infrared surveys have uncovered a large number of cool
brown dwarfs, extending the temperature sequence down to less than 500 K and
constraining the faint end of the luminosity function. One interesting
implication of the derived luminosity function is that the brown dwarf census
in the immediate (<10 pc) solar neighborhood is still largely incomplete, and
some bright (J<16) brown dwarfs remain to be identified in existing surveys.
These objects are especially interesting as they are the ones that can be
studied in most detail, especially with techniques that require large fluxes
(e.g. time-variability, polarimetry, high-resolution spectroscopy) that cannot
realistically be applied to objects uncovered by deep surveys. By
cross-matching the DENIS and the 2MASS point-source catalogs, we have
identified an overlooked brown dwarf -DENIS J081730.0-615520- that is the
brightest field mid-T dwarf in the sky (J = 13.6). We present astrometry and
spectroscopy follow-up observations of this brown dwarf. Our data indicate a
spectral type T6 and a distance -from parallax measurement- of 4.9\pm0.3 pc,
placing this mid-T dwarf among the 3 closest isolated brown dwarfs to the Sun.
