Normalized Lyman-α light curves of GJ 436 from COS (this work) and STIS (Lavie et al. 2017) observations. The baseline fluxes used for normalization were measured in phases outside the [−3, +24] h range. In the case of COS spectra, we measured the baseline flux from the out-of-transit exposures from program GO-15174. The uncertainties of the baseline flux were propagated to the final uncertainties of the normalized fluxes. Left panel: light curve of the Lyman-α reference farwing fluxes, measured in the passbands I and V from Fig. 9.