An Age Constraint for the Very Low-Mass Stellar/Brown Dwarf Binary 2MASS J03202839-0446358AB

Understand

2MASS J03202839-0446358AB is a recently identified, late-type M dwarf/T dwarf spectroscopic binary system for which both the radial velocity orbit for the primary and spectral types for both components have been determined.

• By combining these measurements with predictions from four different sets of evolutionary models, we determine a minimum age of 2.0+/-0.3 Gyr for this system, corresponding to minimum primary and secondary masses of 0.080 Msun and 0.053 Msun, respectively.
• We find broad agreement in the inferred age and mass constraints between the evolutionary models, including those that incorporate atmospheric condensate grain opacity; however, we are not able to independently assess their accuracy.
• The inferred minimum age agrees with the kinematics and absence of magnetic activity in this system, but not the rapid rotation of its primary, further evidence of a breakdown in angular momentum evolution trends amongst the lowest luminosity stars.