H and K Ca ii lines of the eight planet-host stars on the averaged SOPHIE spectra. The stars are sorted by increasing activity from bottom to top, with the values overplotted on the right. The flux of HD 35759 is the correct one; each star plotted above is successively shifted by 1 on the y-scale for visibility reasons. Only HD 12484 and HIP 65407 show visually significant chromospheric emissions.