Significance analysis for potential water vapour cross-correlation signals on the night of February 02, 2017. Top panel: signal-to-noise ratio map as a function of radial velocity in the exoplanet’s rest frame (v_rest, horizontal axis) and the projected orbital velocity semi-amplitude, K_p (vertical axis). Horizontal red lines denote the expected K_p, and vertical red lines mark the expected zero velocity, assuming eccentric orbits. Bottom panel: one-dimensional cross-correlation function at the expected K_p (102.3 km s⁻¹) of GJ436 b for the eccentric case.