Flux densities of the red vs blue lobe measured at 23 epochs with ALLWISE and NEOWISE. The Spitzer measurement is not shown. The black symbols indicate the observed fluxes, $S_{\nu }^{\text{B}}$ and $S_{\nu }^{\text{R}}$. The red symbols denote the fluxes $S_{\nu }^{\text{B}\prime }$ and $S_{\nu }^{\text{R}\prime }$, corrected for periodic oscillations using Eqs. (9) and (10). The solid lines are linear fits to the points of the same colour, and the dashed lines indicate the corresponding uncertainties.