The discovery of the T8.5 dwarf UGPS J0521+3640
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Author
Burningham, B.
Lucas, P.W.
Leggett, S.K.
Smart, R.
Baker, D.
Pinfield, D.J.
Tinney, C. G.
Homeier, D.
Allard, F.
Zhang, Z. H.
Gomes, J.
Day-Jones, A. C.
Jones, H.R.A.
Kovacs, G.
Lodieu, N.
Marocco, F.
Murray, D. N.
Sipocz, B.
Attention
2299/6446
Abstract
We have carried out a search for late-type T dwarfs in the UKIRT Infrared Deep Sky Survey Galactic Plane Survey 6th Data Release. The search yielded two persuasive candidates, both of which have been confirmed as T dwarfs. The brightest, UGPS J0521+3640, has been assigned the spectral type T8.5 and appears to lie at a distance of 7-9 pc. The fainter of the two, UGPS J0652+0324, is classified as a T5.5 dwarf and lies at an estimated distance of 28-37 pc. Warm-Spitzer observations in IRAC channels 1 and 2, taken as part of the GLIMPSE360 Legacy Survey, are available for UGPS J0521+3640 and we used these data with the near-infrared spectroscopy to estimate its properties. We find best-fitting solar metallicity BT-Settl models for T-eff = 600 and 650 K and log g = 4.5 and 5.0. These parameters suggest a mass between 14 and 32M(J) for an age between 1 and 5 Gyr. The proximity of this very cool T dwarf, and its location in the Galactic plane, makes it an ideal candidate for high-resolution adaptive optics imaging to search for cool companions.