Context : We have analyzed a broad-band optical and near-infrared spectrum of FU Tau A , a presumed young brown dwarf in the Taurus star forming region that has intrigued both theorists and observers by its overluminosity in the HR diagram with respect to standard pre-main sequence evolutionary models .
FU Tau A is brighter than any other Taurus member of same or similar spectral type , and various phenomena ( accretion , activity , binarity ) have been put forth as a possible explanation .
The new data , obtained with the X-Shooter spectrograph at the Very Large Telescope , include an unprecedented wealth of information on stellar parameters and simultaneously observed accretion and outflow indicators for FU Tau A .
We present the first measurements of gravity ( \log { g } = 3.5 \pm 0.5 ) , radial velocity ( RV = 22.5 \pm 2.9 km/s ) , rotational velocity ( v \sin { i } = 20 \pm 5 km/s ) and lithium equivalent width ( W _ { Li } = 430 \pm 20 mÅ ) for FU Tau A .
From the rotational velocity and the published period we infer a disk inclination of i \lower 4.0 pt \hbox { $ { \buildrel \displaystyle > \over { \sim } } $ } 50 ^ { \circ } .
The lithium content is much lower than theoretically expected for such a young very low mass object , adding another puzzling feature to this object ’ s properties .
We determine the mass accretion rate of FU Tau A from comparison of the luminosities of 24 emission lines to empirical calibrations from the literature and find a mean of \log { \dot { M } _ { acc } } { [ M _ { \odot } / yr ] } = -9.9 with standard deviation \sigma = 0.2 .
The accretion rate determined independently from modeling of the excess emission in the Balmer and Paschen continua is consistent with this value .
The corresponding accretion luminosity is too small to make a significant contribution to the bolometric luminosity .
Strong magnetic activity affecting the stellar parameters or binarity of FU Tau A , both combined with extreme youth , may be responsible for its position in the HR diagram .
The existence of an outflow in FU Tau A is demonstrated through the first detection of forbidden emission lines from which we obtain an estimate for the mass loss rate , \log { \dot { M } _ { out } } { [ M _ { \odot } / yr ] } < -10.4 .
The mass outflow and inflow rates can be combined to yield \dot { M } _ { out } / \dot { M } _ { acc } \sim 0.3 , a value that is in agreement with jet launching models .

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