Discovery of a Second L Subdwarf in the Two Micron All Sky Survey
  I report the discovery of the second L subdwarf identified in the Two Micron All Sky Survey, 2MASS J16262034+3925190. This high proper motion object (mu = 1.27+/-0.03 "/yr) exhibits near-infrared spectral features indicative of a subsolar metallicity L dwarf, including strong metal hydride and H2O absorption bands, pressure-broadened alkali lines, and blue near-infrared colors caused by enhanced collision-induced H2 absorption. This object is of later type than any of the known M subdwarfs, but does not appear to be as cool as the apparently late-type sdL 2MASS 0532+8246. The radial velocity (Vrad = -260+/-35 km/s) and estimated tangential velocity (Vtan ~ 90-210 km/s) of 2MASS 1626+3925 indicate membership in the Galactic halo, and this source is likely near or below the hydrogen burning minimum mass for a metal-poor star. L subdwarfs such as 2MASS 1626+3925 are useful probes of gas and condensate chemistry in low-temperature stellar and brown dwarf atmospheres, but more examples are needed to study these objects as a population as well as to define a rigorous classification scheme. 
Adam J. Burgasser