On the occurrence of a shock wave in the atmosphere of rho Puppis

New high temporal and spectral resolution observations of the Ca II K absor ption profile of the delta Scuti star rho Puppis are presented. The data co ver 1.2 pulsation cycle. Contrary to the result of Dravins et al. (1977), t he line profile corresponding to the phase just before the maximum accelera tion (monitored twice here), does not show any emission feature. Thus, the Ca II K emission may be of transient nature. Consequently, the intensity of the shock wave should be weak and strongly variable. This result is consis tent with a previous study (Mathias et al. 1997) where no shock wave signat ure was present in the H alpha and metallic line profiles observed. Thus, a dditional observations are required to specify the frequency of occurrence of the transient emission.