SSPMJ1102-3431 brown dwarf characterization from accurate proper motion   and trigonometric parallax
  In 2005, Scholz and collaborators (Scholz et al. 2005) discovered, in a proper motion survey, a young brown dwarf SSSPMJ1102-3431(SSSPMJ1102) of spectral type M8.5, probable member of the TW Hydrae Association (TWA) and possible companion of the T Tauri star TW Hya. The physical characterization of SSSPMJ1102 was based on the hypothesis that it forms a binary system with TW Hya. The recent discovery of a probable giant planet inside the TW Hya protoplanetary disk with a very short-period (Setiawan et al. 2008) and a disk around SSSPMJ1102 (Riaz and Gizis 2008) make it especially interesting and important to measure well the physical parameters of SSSPMJ1102. Trigonometric parallax and proper motion measurements of SSSPMJ1102 are necessary to test for TWA membership and, thus, to determine the mass and age of this young brown dwarf and the possibility that it forms a wide binary system with TW Hya. Two years of regular observations at the ESO NTT/SUSI2 telescope, have enabled us to determine the trigonometric parallax and proper motion of SSSPMJ1102. Our parallax and proper motion determination allow us to precisely describe the physical properties of this low mass object and to confirm its TWA membership. Our results are not incompatible with the hypothesis that SSSPMJ1102 is a binary companion of the star TW Hya. 
R. Teixeira, C. Ducourant, G. Chauvin, A. Krone-Martins, I. Song and   B. Zuckerman