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Evolutionary models are widely used to infer the mass of stars, brown dwarfs,and giant planets. Their predictions are thought to be less reliable at youngages ($<$ 200 Myr) and in the low-mass regime ($\mathrm{<1~M_{\odot}}$). GJ2060 AB and TWA 22 AB are two rare astrometric M-dwarf binaries respectivelymembers of the AB Doradus and Beta Pictoris moving groups. As their dynamicalmass can be measured within a few years, they can be used to calibrate theevolutionary tracks and set new constraints on the age of young moving groups.We find a total mass of $\mathrm{0.18\pm 0.02~M_\odot}$ for TWA 22. That massis in good agreement with model predictions at the age of the Beta Pic movinggroup. We obtain a total mass of $\mathrm{1.09 \pm 0.10~M_{\odot}}$ for GJ2060. We estimate a spectral type of M$1\pm0.5$,$\mathrm{L/L_{\odot}=-1.20\pm0.05}$ dex, and $\mathrm{T_{eff}=3700\pm100}$ Kfor GJ 2060 A. The B component is a M$3\pm0.5$ dwarf with$\mathrm{L/L_{\odot}=-1.63\pm0.05}$ dex and $\mathrm{T_{eff}=3400\pm100}$ K.The dynamical mass of GJ 2060 AB is inconsistent with the most recent modelspredictions (BCAH15, PARSEC) for an ABDor age in the range 50-150 Myr. It is 10to 20\% (1-2 sigma, depending on the assumed age) above the models predictions,corresponding to an underestimation of $0.10$ to $0.20~\mathrm{M_\odot}$.Coevality suggests a young age for the system ($\sim$ 50 Myr) according to mostevolutionary models. TWA 22 validates the predictions of recent evolutionarytracks at $\sim$20 Myr. On the other hand, we evidence a 1-2 sigma mismatchbetween the predicted and observed mass of GJ 2060 AB. This slight departuremay indicate that one of the star hosts a tight companion. Alternatively, thiswould confirm the models tendency to underestimate the mass of young low-massstars.

Dynamical masses of M-dwarf binaries in young moving groups: I - The case of TWA 22 and GJ 2060