Orbital radial variation (Δ(R_mean-R_GC)) versus galactocentric distance (RGC) of our sample stars. Target sample stars are colour- and size-coded by the eccentricity of their orbit. The red line marks a null difference between the R_mean of the orbit and the current R_GC, while the green lines indicate a positive difference of 1 kpc (stars that likely migrated from the outer disc have Δ > 1 kpc) and a negative difference of −1 kpc (stars that likely migrated from the inner disc have Δ < − 1 kpc).