Medium-resolution infrared integral field spectroscopy of the brown dwarf TWA 5 B

We obtained medium-resolution infrared K-band integral field spectroscopy with VLT/Sinfoni for the brown dwarf TWA 5 B, a companion to the weak-line T Tauri star TWA 5 in the TW Hya association. We compare the final spectrum with theoretical model atmospheres from DRIFT-PHOENIX (Dehn et al. 2007, Helling et al. 2008 ab, Witte 2008) for temperature from 2000 to 3100 K, gravity log g = 3.0, 3.5, and 4.0 g (g in cm/s(2)) and metallicity -0.5, 0.0 (solar), and 0.5; we also varried the extinction towards TWA 5 B while searching for the best-fit model between A(V) - 0.0 and 15 nag. The best-fitting model spectrum yields the following parameters for TWA 5 B: Effective temperature T-eff similar or equal to 2800 K. tnctallicity [M/H] similar or equal to -0.5 (for metal content M), surface gravity log g similar or equal to 4.0 and extinction A(V) - 0.0 mag. From those parameters and the distance towards TWA (similar to 65 pc), we can compute the mass of the brown dwarf to be roughly 25 Jupiter masses, but with large error bars including massive planets and low-mass stars. Given its projected separation from the primary star, similar to 123 AU, it has certainly more likely formed star-like. i.e. being a brown dwarf companion.