DISCOVERY OF AN UNUSUALLY RED L-TYPE BROWN DWARF

We report the discovery of an unusually red brown dwarf found in a search for high proper motion objects using WISE and 2MASS data. WISEP J004701.06+680352.1 is moving at 0 ''.44 yr(-1) and lies relatively close to the Galactic plane (b = 5 degrees.2). Near-infrared photometry and spectroscopy reveals that this is one of the reddest (2MASS J - K-s = 2.55 +/- 0.08 mag) field L dwarfs yet detected, making this object an important member of the class of unusually red L dwarfs. We discuss evidence for thick condensate clouds and speculate on the age of the object. Although models by different research groups agree that thick clouds can explain the red spectrum, they predict dramatically different effective temperatures, ranging from 1100 K to 1600 K. This brown dwarf is well suited for additional studies of extremely dusty substellar atmospheres because it is relatively bright (K-s = 13.05 +/- 0.03 mag), which should also contribute to an improved understanding of young gas-giant planets and the transition between L and T brown dwarfs.