Lyα light curve of GJ 436 obtained from integrating the raw spectra uncorrected for systematics. The flux is integrated over the blue wing [− 120,−40] km s^-1 (a), the red wing [+ 30, + 120] km s^-1 (b), the reference band [− 250,−120] ∪ [ + 120, + 250] km s^-1 (c), and the [− 50,50] km s^-1 band of the Si iii line (d). The colour code is the same as in Fig. 1. Large coloured symbols with errors bars are the individual HST orbits (see Table A.1 for the visit symbols) while small grey circles are the time-tagged sub-exposures extracted from each HST orbit for panel a, b, and c.