A 2MASS L dwarf companion to the nearby K dwarf GJ 1048

We report the discovery of a probable L1 companion to the nearby K2 dwarf GJ 1048 using the Two Micron All-Sky Survey (2MASS). This source, 2MASSI J0235599-233120, or GJ 1048B, has 2MASS near-infrared colors and absolute magnitudes consistent with an early L dwarf companion with a projected separation of 250 AU. The L1 spectral type is confirmed by far-red optical and low-resolution IR spectroscopy. We present evidence that GJ 1048 is a young (less than or similar to1 Gyr) system, and that GJ 1048B may be a high-mass brown dwarf below the hydrogen burning limit. Additional studies of the GJ 1048 system will help constrain the characteristics of L dwarfs as a function of age and mass.