Intrinsic Ly-α line profile of TRAPPIST-1 (orange line). The solid blue line shows the Ly-α line profile after absorption by the ISM hydrogen and deuterium (dotted black line). The solid black line shows the line profile convolved with STIS LSF and compared to the observations shown as a red histogram. Hatched regions were excluded from the fit. The right axis shows the ratio β between radiation pressure and stellar gravity.