Left: old and new observations adjusted. The dotted line represents the solution based upon Luhman (2013) and Mamajek (2013). The black continuous line represents the motion of the barycentre from our solution. The inset zooms onto the region covered by the FORS2 observations. The red (resp. blue) line represents the motion of the L (resp. T) dwarf. Middle: relative positions obtained with FORS2 during our two-month monitoring campaign and the best parabolic fits. Right: residuals of the FORS2 data based on the parabolic fit.