Heat redistribution efficiency ε as a functionof the geometric albedo A_g. The median value of ε is represented by the blue curve and the shaded areas highlight the 1 σ, 2 σ, and 3 σ uncertainty range. The value of ε is computed as the nightside-to-dayside flux ratio measured by CHEOPS. Low values of A_g indicates low reflectivity and a phase-curve amplitude mostly due to thermal emission. The thermal contribution gets smaller for higher A_g where reflected light starts to be important.