Trajectory of the RG lobe DA240 in the U_e − U_B plane calculated with B_μ = 1.5 (which fits the radio spectrum with p₁ = 1) for decreasing values of p₁ = 10³ − 1 (from left to right) is shown by the red open circles. The results of Isobe et al. (2009, 2011a,b) for the GRGs DA240E, 3C 35 and 3C 326W assuming p₁ = 10³ are shown by the cyan dots. RG lobes from the analysis of Croston et al. (2005) obtained assuming α = 2 and p₁ = 10 for all lobes are also shown as green dots: filled dots refer to lobes with reliable X-ray spectral estimates. Note these last data are not directly comparable to those of Isobe et al. (2009, 2011a,b) for GRGs.