Spectral energy distribution of the planet WASP-189 b. The high-resolution synthetic SED computed with HELIOS (Malik et al. 2017, 2019) is represented in light blue and assumes the irradiating power is fully absorbed and not redistributed (A_B = ε = 0). The dark blue line is the HELIOS data averaged over bins of 5 nm. The black-body profile of the maximum dayside temperature T_{day, max} is shown inorange. We note that accounting for emission lines in the planetary spectrum leads to a different SED with respectto the black-body approximation, with more energy in the blue end. This affects the flux measured in the CHEOPS passband (black dotted line), with the dayside of WASP-189 b appearing slightly brighter.