Discovery of the benchmark metal-poor T8 dwarf BD +01° 2920B
Marocco, F.; Homeier, D.; Pinfield, D. J.; Jones, H. R. A.; Lodieu, N.; Zhang, Z. H.; Gálvez-Ortiz, M. C.; Lucas, P. W.; Leggett, S. K.; Tinney, C. G.; Smith, L.; Jenkins, J. S.; van Spaandonk, L.; Burningham, B.; Smart, R.; Gomes, J.; Day-Jones, A. C.; Murray, D. N.; Katsiyannis, A. C.; Catalan, S.; Cardoso, C.; Clarke, J. R. A.; Folkes, S.
United Kingdom, Spain, United States, Australia, Italy, Chile, Greece, France
Abstract
We have searched the Wide-field Infrared Survey Explorer first data release for widely separated (≤10 000 au) 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 17.2 pc. This new benchmark has Teff= 680 ± 55 K 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 J075003.84+272544.8.