The Missing Link: Early Methane ("T") Dwarfs in the Sloan Digital Sky Survey.
We report the discovery of three cool brown dwarfs that fall in the effective temperature gap between the latest L dwarfs currently known, with no methane absorption bands in the 1-2.5 µm range, and the previously known methane (T) dwarfs, whose spectra are dominated by methane and water. The newly discovered objects were detected as very red objects in the Sloan Digital Sky Survey imaging data and have JHK colors between the red L dwarfs and the blue Gl 229B-like T dwarfs. They show both CO and CH(4) absorption in their near-infrared spectra in addition to H(2)O, with weaker CH(4) absorption features in the H and K bands than those in all other methane dwarfs reported to date. Due to the presence of CH(4) in these bands, we propose that these objects are early T dwarfs. The three form part of the brown dwarf spectral sequence and fill in the large gap in the overall spectral sequence from the hottest main-sequence stars to the coolest methane dwarfs currently known.
Leggett
SK
Geballe
TR
Fan
X
Schneider
DP
Gunn
JE
Lupton
RH
Knapp
GR
Strauss
MA
McDaniel
A
Golimowski
DA
Henry
TJ
Peng
E
Tsvetanov
ZI
Uomoto
A
Zheng
W
Hill
GJ
Ramsey
LW
Anderson
SF
Annis
JA
Bahcall
NA
Brinkmann
J
Chen
B
Csabai
I
Fukugita
M
Hennessy
GS
Hindsley
RB
Ivezic
Z
Lamb
DQ
Munn
JA
Pier
JR
Schlegel
DJ
Smith
JA
Stoughton
C
Thakar
AR
York
DG