Semi-secular phase portrait of 2014 FZ₇₁. On the right axis, the values of a corresponding to Σ are shown. The blue crosses come from the filtered output of the full non-averaged numerical integration (same as Fig. 1), with the current position of 2014 FZ₇₁ on the big spot. For comparison, the 1-sigma error bar of the (osculating) orbital solution is added. The uncertainty is compatible with the red hatched area inside the resonance, from which we get a possible value of the parameter J. The same method was used in Saillenfest et al. (2017), but it was not restricted to the uncertainty ranges.