The discrepancy between dynamical and theoretical mass in the triplet-system 2MASS J10364483+1521394

We combine new Lucky Imaging astrometry from NTT/AstraLux Sur with already published astrometry from the AstraLux Large M-dwarf Multiplicity Survey to compute orbital elements and individual masses of the 2MASS J10364483+1521394 triple system belonging to the Ursa-Major moving group. The system consists of one primary low-mass M-dwarf orbited by two less massive companions, for which we determine a combined dynamical mass of $M_{\rm{B}+\rm{C}}= 0.48 \pm 0.14
M_\odot$. We show from the companions relative motions that they are of equal mass (with a mass ratio of $1.00\pm 0.03$), thus $0.24\pm 0.07M_{\odot }$ individually, with a separation of 3.2 \pm 0.3\AU and conclude that these masses are significantly higher ($30\mathrm{\%}$) than what is predicted by theoretical stellar evolutionary models. The biggest uncertainty remains the distance to the system, here adopted as $20.1\pm 2.0$ pc based on trigonometric parallax, whose ambiguity has a major impact on the result. With the new observational data we are able to conclude that the orbital period of the BC pair is 8.41^{+0.04}_{-0.02}\years.