Left: secondary eclipse spectrum models of TRAPPIST-1b for different assumptions on its atmospheric composition, as simulated by Lincowski et al. (2018), over-plotted with our empirical value, derived from the global analysis of 28 occultations observed with Spitzer IRAC/channel 2 (centered in 4.5 μm), the error barshown corresponds to the 3-σ confidence interval of the measurement. The y-axis has a logarithmic scale. The shade gray band stands for the zone where a spectral absorption from CO₂ molecule – if present in the atmosphere – is expected. Right: similar but for TRAPPIST-1c.