Discovery of the benchmark metal poor T8 dwarf BD+01 2920B
van Spaandonk, L.
Katsiyannis, A. C.
We have searched the Wide-field Infrared Survey Explorer 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 J142320.86+011638.1 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 20-50MJup. 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 J07003.84+272544.8