The discovery of the T8.5 dwarf UGPS J0521+3640
Burningham, Ben; 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.
Citation: 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 2011 , ' The discovery of the T8.5 dwarf UGPS J0521+3640 ' Monthly Notices of the Royal Astronomical Society , vol 414 , no. 1 , pp. L90-L94 . , 10.1111/j.1745-3933.2011.01062.x
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.
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