Discovery of X-ray emission from the eclipsing brown-dwarf binary 2MASS   J05352184-0546085
  The eclipsing brown-dwarf binary system 2MASS J05352184-0546085 is a case sui generis. For the first time, it allows a detailed analysis of the individual properties of young brown dwarfs, in particular, masses, and radii, and the temperature ratio of the system components can be determined accurately. The system shows a "temperature reversal" with the more massive component being the cooler one, and both components are found to be active. We analyze X-ray images obtained by Chandra and XMM-Newton containing 2MASS J05352184-0546085 in their respective field of view. The Chandra observatory data show a clear X-ray source at the position of 2MASS J05352184-0546085, whereas the XMM-Newton data suffer from contamination from other nearby sources, but are consistent with the Chandra detection. No indications of flaring activity are found in either of the observations (together about 70 ks), and we thus attribute the observed flux to quiescent emission. With an X-ray luminosity of 3*10^{28} erg/s we find an L_X/L_{bol}-ratio close to the saturation limit of 10^{-3} and an L_{X}/L_{H\alpha}-ratio consistent with values obtained from low-mass stars. The X-ray detection of 2MASS J05352184-0546085 reported here provides additional support for the interpretation of the temperature reversal in terms of magnetically suppressed convection, and suggests that the activity phenomena of young brown dwarfs resemble those of their more massive counterparts. 
S. Czesla, P.C. Schneider, J.H.M.M. Schmitt