TY - JOUR
T1 - An improved red spectrum of the methane or T dwarf SDSS 1624+0029
T2 - The role of the alkali metals
AU - Liebert, James
AU - Reid, I. Neill
AU - Burrows, Adam
AU - Burgasser, Adam J.
AU - Kirkpatrick, J. Davy
AU - Gizis, John E.
N1 - Funding Information:
This research is supported by a NASA JPL grant (961040NSF) which permits us to undertake a core science project on very low mass objects discovered in the 2MASS survey. A. B. acknowledges support from NASA grants NAG5-7499 and NAG5-7073. The model curve was computed based upon a temperature/pressure profile generated by M. Marley and the models in Burrows et al. (1997). We wish to acknowledge helpful suggestions from an anonymous referee.
PY - 2000/4/20
Y1 - 2000/4/20
N2 - A Keck II low-resolution spectrum shortward of 1 μm is presented for SDSS 1624+0029, the first field methane or T dwarf discovered in the Sloan Digital Sky Survey. Significant flux is detected down to the spectrum's short-wavelength limit of 6200 Å. The spectrum exhibits a broad absorption feature centered at 7700 Å, which we interpret as the K I λλ7665, 7699 resonance doublet. The observed flux declines shortward of 7000 Å, most likely owing to the red wing of the Na I doublet. Both Cs I doublet lines are detected more strongly than in an earlier red spectrum. Neither Li I absorption nor Hα emission are detected. An exploratory model fit to the spectrum suggests that the shape of the red spectrum can be primarily accounted for by the broad wings of the K I and Na I doublets. This behavior is consistent with the argument proffered by Burrows, Marley, & Sharp that strong alkali absorption is principally responsible for depressing T dwarf spectra shortward of 1 μm. In particular, there seems no compelling reason at this time to introduce dust or an additional opacity source in the atmosphere of the Sloan object. The width of the K I and strengths of the Cs I lines also indicate that the Sloan object is warmer than Gl 229B.
AB - A Keck II low-resolution spectrum shortward of 1 μm is presented for SDSS 1624+0029, the first field methane or T dwarf discovered in the Sloan Digital Sky Survey. Significant flux is detected down to the spectrum's short-wavelength limit of 6200 Å. The spectrum exhibits a broad absorption feature centered at 7700 Å, which we interpret as the K I λλ7665, 7699 resonance doublet. The observed flux declines shortward of 7000 Å, most likely owing to the red wing of the Na I doublet. Both Cs I doublet lines are detected more strongly than in an earlier red spectrum. Neither Li I absorption nor Hα emission are detected. An exploratory model fit to the spectrum suggests that the shape of the red spectrum can be primarily accounted for by the broad wings of the K I and Na I doublets. This behavior is consistent with the argument proffered by Burrows, Marley, & Sharp that strong alkali absorption is principally responsible for depressing T dwarf spectra shortward of 1 μm. In particular, there seems no compelling reason at this time to introduce dust or an additional opacity source in the atmosphere of the Sloan object. The width of the K I and strengths of the Cs I lines also indicate that the Sloan object is warmer than Gl 229B.
KW - Stars: atmospheres
KW - Stars: low-mass, brown dwarfs
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U2 - 10.1086/312619
DO - 10.1086/312619
M3 - Article
C2 - 10770713
AN - SCOPUS:0034689830
SN - 0004-637X
VL - 533
SP - L155-L158
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2 PART 2
ER -