An improved red spectrum of the methane or T dwarf SDSS 1624+0029: The role of the alkali metals

被引:47
作者
Liebert, J [1 ]
Reid, IN
Burrows, A
Burgasser, AJ
Kirkpatrick, JD
Gizis, JE
机构
[1] Univ Arizona, Dept Astron, Tucson, AZ 85721 USA
[2] Univ Arizona, Steward Observ, Tucson, AZ 85721 USA
[3] Univ Penn, Dept Phys & Astron, Philadelphia, PA 19104 USA
[4] CALTECH, Div Phys, Pasadena, CA 91125 USA
[5] CALTECH, Ctr Infrared Proc & Anal, Pasadena, CA 91125 USA
关键词
stars : atmospheres; stars : individual (SDSS 1624+0029); stars; low-mass; brown dwarfs;
D O I
10.1086/312619
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
A Keek II low-resolution spectrum shortward of 1 mu m 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 Angstrom. The spectrum exhibits a broad absorption feature centered at 7700 Angstrom, which we interpret as the K I lambda lambda 7665, 7699 resonance doublet. The observed flux declines shortward of 7000 Angstrom, 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 H alpha 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 mu m. 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 G1 229B.
引用
收藏
页码:L155 / L158
页数:4
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