Median of the marginalised posterior distributions of γ_GWB and log₁₀A_GWB of all the 100 simulations (shaded region), posterior distribution of realisation 94 (solid line) and principal axis evaluated orientation evaluated from the Fisher matrix (dashed line). Panel (a): comparison between DR2full and DR2 5yr. For comparison, the principal axes of the real EPTA DR2full and MeerKAT PTA are also shown. Panel (b): comparison between DR2* 5yr and DR2 5yr. For reference, the injected value is displayed as a black cross.