Detection of strong activity in the eclipsing binary brown dwarf 2MASS J05352184-0546085: a possible explanation for the temperature reversal

We show high-resolution spectra of the eclipsing brown dwarf binary 2MASS J05352184 - 0546085 taken at the two opposite radial velocity maxima. Comparisons of the TiO bands to model and template spectra are fully consistent with the temperatures previously derived for this system. In particular, the reversal of temperatures with mass - in which the higher mass primary is cooler than its companion - is confirmed. We measure the projected rotation velocities of the components; the primary is rotating at least twice as rapidly as the secondary. At the two radial velocity maxima, H alpha emission lines of both components stick out to either sides of the H alpha central wavelength, which is dominated by nebula emission. This enables us to model the individual H alpha lines of the primary and the secondary. We find that the H alpha emission from the primary is at least 7 times stronger than the emission from the secondary. We conclude that the temperature reversal is very likely due to strong magnetic fields inhibiting convection on the primary.