Time sequence of the residual spectra around the He  I triplet, after removal of the stellar and telluric absorption and the sky emission lines, with the relative flux indicated in greyscale. The radial velocity in the stellar rest-frame is on the horizontal axis, and orbital phase on the vertical axis. The corresponding wavelengths in the rest-frame of the star are indicated in the top axis. The area around orbital phase −0.03 is blanked out due to the lack of observations. The horizontal dashed lines indicate the first, second, third, and fourth contact of the transit, respectively. A helium signal is visible (darker greyscales), following the planet velocity (slanted lines) from −16 to +16 km s⁻¹.