Studies of fundamental parameters of very low-mass objects are indispensable to provide tests of stellar evolution models that are used to derive theoretical masses of brown dwarfs and planets .
However , only objects with dynamically determined masses and precise photometry can effectively evaluate the predictions of stellar models .
AB Dor C ( 0.090 M _ { \odot } ) has become a prime benchmark for calibration of theoretical evolutionary models of low-mass young stars .
One of the ambiguities remaining in AB Dor C is the possible binary nature of this star .
We observed AB Dor C with the VLTI/AMBER instrument in low-resolution mode at the J , H and K bands .
The interferometric observables at the K-band are compatible with a binary brown dwarf system with tentative components AB Dor Ca/Cb with a K-band flux ratio of 5 % \pm 1 % and a separation of 38 \pm 1 mas .
This implies theoretical masses of 0.072 \pm 0.013 M _ { \odot } and 0.013 \pm 0.001 M _ { \odot } for each component , near the hydrogen-burning limit for AB Dor Ca , and near the deuterium-burning limit , straddling the boundary between brown dwarfs and giant planets , for AB Dor Cb .
The possible binarity of AB Dor C alleviates the disagreement between observed magnitudes and theoretical mass-luminosity relationships .