Optical IR (DECam) flux density of eRASSU J060839.5−704014 (blue dots) with the best-fit black-body spectrum in red and a power law overplotted in blue. The UV fluxes from GALEX are plotted as upper limits (in orange) as they were contaminated by a nearby bright object and were not used for the fit. Also overplotted is a black-body spectrum with a temperature of 27 000 K in green, as obtained for the case of the DD system RX J0806.3+1527 (Esposito et al. 2014).