title: The Discovery of a Second Field Methane Brown Dwarf from Sloan Digital Sky Survey Commissioning Data.
abstract: We report the discovery of a second field methane brown dwarf from the commissioning data of the Sloan Digital Sky Survey (SDSS). The object, SDSS J134646.45-003150.4 (hereafter SDSS 1346-00), was selected because of its very red color and stellar appearance. Its spectrum between 0.8 and 2.5 µm is dominated by strong absorption bands of H2O and CH4 and closely mimics those of Gliese 229B and SDSS 162414.37+002915.6 (hereafter SDSS 1624+00), two other known methane brown dwarfs. SDSS 1346-00 is approximately 1.5 mag fainter than Gliese 229B, suggesting that it lies about 11 pc from the Sun. The ratio of flux at 2.1 µm to that at 1.27 µm is larger for SDSS 1346-00 than for Gliese 229B and SDSS 1624+00, which suggests that SDSS 1346-00 has a slightly higher effective temperature than the others. Based on a search area of 130 deg2 and a detection limit of z*=19.8, we estimate a space density of 0.05 pc-3 for methane brown dwarfs with Teff approximately 1000 K in the 40 pc3 volume of our search. This estimate is based on small-sample statistics and should be treated with appropriate caution.
authors.initials: ZI
authors.lastname: Tsvetanov
authors.initials: DA
authors.lastname: Golimowski
authors.initials: W
authors.lastname: Zheng
authors.initials: TR
authors.lastname: Geballe
authors.initials: SK
authors.lastname: Leggett
authors.initials: HC
authors.lastname: Ford
authors.initials: AF
authors.lastname: Davidsen
authors.initials: A
authors.lastname: Uomoto
authors.initials: X
authors.lastname: Fan
authors.initials: GR
authors.lastname: Knapp
authors.initials: MA
authors.lastname: Strauss
authors.initials: J
authors.lastname: Brinkmann
authors.initials: DQ
authors.lastname: Lamb
authors.initials: HJ
authors.lastname: Newberg
authors.initials: R
authors.lastname: Rechenmacher
authors.initials: DP
authors.lastname: Schneider
authors.initials: DG
authors.lastname: York
authors.initials: RH
authors.lastname: Lupton
authors.initials: JR
authors.lastname: Pier
authors.initials: J
authors.lastname: Annis
authors.initials: I
authors.lastname: Csabai
authors.initials: RB
authors.lastname: Hindsley
authors.initials: Z
authors.lastname: Ivesic
authors.initials: JA
authors.lastname: Munn
authors.initials: AR
authors.lastname: Thakar
authors.initials: P
authors.lastname: Waddell