Discovery of the brightest T dwarf in the northern hemisphere

We report the discovery of a bright (H = 12.77) brown dwarf designated SIMP J013656.5 + 093347. The discovery was made as part of a near-infrared proper-motion survey, SIMP (Sondage Infrarouge de Mouvement Propre), which uses proper motion and near-infrared/optical photometry to identify brown dwarf candidates. A low-resolution (lambda/Delta lambda similar to 40) spectrum of this brown dwarf covering the 0.88-2.35 mm wavelength interval is presented. Analysis of the spectrum indicates a spectral type of T2.5 +/- 0.5. A photometric distance of 6.4 +/- 0.3 pc is estimated, assuming it is a single object. Current observations rule out a binary of mass ratio similar to 1 and separation greater than or similar to 5 AU. SIMP J013656.5 + 093347 is the brightest T dwarf in the northern hemisphere and is surpassed only by epsilon Indi Bab over the whole sky. It is thus an excellent candidate for detailed studies and should become a benchmark object for the early T spectral class.