tokens: light. As the equilibrium temperature increases, thermal emission becomes as important as reflected light in that bandpass, leading to a smaller phase curve amplitude since both the dayside and the nightside are emitting light. Then as the equilibrium temperature increases again, the amplitude increases due to the shortening of the radiative time-scale, as in the other phase curves dominated by thermal emission. The third class of behaviour occurs at specific wavelengths that are influenced by exotic chemical effects, where the phase curve amplitude can exhibit non-monotonic behaviour with equilibrium temperature. This occurs in particular in the Spitzer 3.6- and 8-micron bands of Fig. 9 due to methane and CO opacity but will also happen at all wavelengths where a change in chemical composition with temperature leads to a significant opacity variation. For and for , the amplitude of the phase curve rises with equilibrium temperature whereas for the opposite happens. This peculiar behaviour is due to our assumption of local chemical equilibrium that leads to a spatially varying ratio between carbon monoxide and methane molecules on the planet (see also Dobbs-Dixon Cowan 2017 ). Hot Jupiters, however, are not expected to be in local chemical equilibrium since the vertical and horizontal transport of material can be much faster than chemical reactions. In such a case, the system is said to be quenched, and homogeneous chemical abundances are expected at the photosphere (Cooper Showman 2006 ; Visscher Moses 2011 ; Agúndez et al. 2014 ; Drummond et al. 2018a , 2020 ; Steinrueck et al. 2019 ). If quenching happens, and as long as CO is the dominant species (rather than CH 4 ), then the amplitude of the phase curve should be monotonically increasing with equilibrium temperature at all wavelengths dominated by thermal emission. 6.1.2 Phase curve offset The offset of the phase curve maximum is shown in the bottom panels of Fig. 9 . It always follows a bell curve, with an offset that increases with equilibrium temperature at low equilibrium temperatures and an offset that decreases with equilibrium temperature at larger equilibrium temperatures. Whereas the decrease of the offset with increasing temperature is expected based on the radiative and advective time-scales shown in Fig. 4 , the low-temperature behaviour is more puzzling, but is consistent with some of the cases explored in fig. 9 of Komacek et al. ( 2017 ) Again, the Kepler bandpass stands apart. At low temperatures, when the light curve is dominated by reflected light, the amplitude is large and the offset is close to zero because Rayleigh scattering is approximately homogeneous over the dayside of the planet. As the equilibrium temperature increases, thermal emission becomes more and more important compared to Rayleigh scattering, leading to an offset that increases with increasing equilibrium temperature. Above , the decrease of the radiative time-scale with equilibrium temperature
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