2010ApJ...713.1249M

Dynamical masses have been obtained by Dupuy et al. for the brown dwarf binary HD 130948BC. The components have luminosities log (L/L_☉) of -3.82 and -3.90, and masses of 0.0555 and 0.0530 M_☉. In a luminosity-age diagram, Dupuy et al. found that L_bol for both B and C are brighter than theoretical tracks by factors of 2-3, if the age of the system is as old as their estimate of 0.79 Gyr (based on gyrochronology). Here, we apply our model of magnetic convection, in which the onset of convection is impeded in the presence of a vertical magnetic field: our goal is to replicate the observed properties not only in the luminosity-age diagram, but simultaneously in the T_eff-age diagram and in the H-R diagram. Expressing the internal magnetic pressure as a fraction δ of the gas pressure, we obtain evolutionary tracks which fit both stars in an H-R diagram provided that δ lies in the range 0.007-0.038. With such values of δ, our models replicate the observed luminosities of both B and C, provided that the age is no larger than ∼0.39 Gyr. This is significantly younger than the mean age estimated by Dupuy et al. for the primary star in the system, HD 130948A. However, there is sufficient uncertainty in the empirical parameters that an age as young as the one suggested by our magnetic models (∼0.39 Gyr) is marginally within the permitted range.