* Astronomy

Blobrana · L

RE: BD+01 2920B

Blobrana · L

Title: Discovery of the benchmark metal poor T8 dwarf BD+01 2920B
Authors: D. J. Pinfield, B. Burningham, N. Lodieu, S. K. Leggett, C. G. Tinney, L. van Spaandonk, F. Marocco, R. Smart, J. Gomes, L. Smith, P. W. Lucas, A. C. Day-Jones, D. N. Murray, A. C. Katsiyannis, S. Catalan, C. Cardoso, J. R. A. Clarke, S. Folkes, M. C. Galvez-Ortiz, D. Homeier, J. S. Jenkins, H. R. A. Jones, Z. H. Zhang

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.