Astronomy and Astrophysics, volume 482, 961-971 (2008/5-2)
CFBDS J005910.90-011401.3: reaching the T-Y brown dwarf transition?
DELORME P., DELFOSSE X., ALBERT L., ARTIGAU E., FORVEILLE T., REYLE C., ALLARD F., HOMEIER D., ROBIN A.C., WILLOTT C.J., LIU M.C. and DUPUY T.J.
Abstract (from CDS):
We report the discovery of CFBDS J005910.90-011401.3
), the coolest brown dwarf identified to date. We found CFBDS0059
using i' and z' images from the Canada-France-Hawaii Telescope (CFHT), and present optical and near-infrared photometry, Keck laser-guide-star adaptive optics imaging, and a complete near-infrared spectrum, from 1.0 to 2.2µm. A side-to-side comparison of the near-infrared spectra of CFBDS0059
and ULAS J003402.77-005206.7
), previously the coolest known brown dwarf, indicates that CFBDS0059
is ∼50±15K cooler. We estimate a temperature of Teff
∼620K and gravity of logg∼4.75. Evolutionary models translate these parameters into an age of 1-5Gyr and a mass of 15-30MJup
. We estimate a photometric distance of ∼13pc, which puts CFBDS0059
within easy reach of accurate parallax measurements. Its large proper motion suggests membership in the older population of the thin disk. The spectra of both CFBDS0059
and ULAS J0034 show probable absorption by a wide ammonia band on the blue side of the H-band flux peak. If, as we expect, that feature deepens further for still lower effective temperatures, its appearance will become a natural breakpoint for the transition between the T spectral class and the new Y spectral type. Together, CFBDS0059
and ULAS J0034 would then be the first Y0 dwarfs.
techniques: spectroscopic - surveys - stars: atmospheres - infrared: stars - stars: low-mass, brown dwarfs
Text: CFBDS JHHMMSS.ss+DDMMSS.s N=2 = CFBDS JHHMMSS+DDMMSS N=2.
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