2mass J22521073 1730134: a Resolved L/t Binary at 14 Parsecs

NICMOS images of the nearby late-type L dwarf 2MASS J22521073 1730134 (DENIS-P J225210.73 173013.4) show that it is a close double, separation 0B13. The companion is 1.0 mag fainter than the primary in the F110W passband and 1.55 mag fainter in the F170M images. The latter passband is centered on the 1.6 mmethane band. The small separation and the absence of an optical counterpart suggest that the two sources are associated; the relatively blue infrared color suggests that 2MASS J22521073 1730134B is a T-type binary companion of the late-L primary. This hypothesis is supported by infrared spectroscopy, which shows weak methane absorption in both theH and K passbands. We estimate a distance of 13:6þ3:8 2:6 pc to the system and a projected linear separation of 1.75 AU. We consider the potential for measuring dynamical masses of the two components. Subject headings: binaries: visual — stars: individual (2MASSW J22521073 1730134) — stars: low-mass, brown dwarfs