We have searched the WISE first data release for widely separated (<10,000AU) late T dwarf companions to Hipparcos and Gliese stars. We have discovered a new binary system containing a K-band suppressed T8p dwarf WISEP J1423+0116 and the mildly metal poor ([Fe/H]=-0.38+-0.06) primary BD+01 2920 (Hip 70319), a G1 dwarf at a distance of 17.2pc. This new benchmark has Teff=680+-55K and a mass of 20-50 Mjup. Its spectral properties are well modelled except for known discrepancies in the Y and K bands. Based on the well determined metallicity of its companion, the properties of BD+01 2920B imply that the currently known T dwarfs are dominated by young low-mass objects. We also present an accurate proper motion for the T8.5 dwarf WISEP J075003.84+272544.8.
@article{arxiv.1201.3243,
title = {Discovery of the benchmark metal poor T8 dwarf BD+01 2920B},
author = {D. J. Pinfield and B. Burningham and N. Lodieu and S. K. Leggett and C. G. Tinney and L. van Spaandonk and F. Marocco and R. Smart and J. Gomes and L. Smith and P. W. Lucas and A. C. Day-Jones and D. N. Murray and A. C. Katsiyannis and S. Catalan and C. Cardoso and J. R. A. Clarke and S. Folkes and M. C. Galvez-Ortiz and D. Homeier and J. S. Jenkins and H. R. A. Jones and Z. H. Zhang},
journal= {arXiv preprint arXiv:1201.3243},
year = {2015}
}