SIMBAD references

New high temporal and spectral resolution observations of BW Vul are presented. The line doubling phases, occurring twice per pulsation cycle during the velocity discontinuities, are interpreted in terms of shock waves. The first and largest doubling is seemingly due to the formation of a shock wave during the supersonic infalling motion of the atmosphere. The famous observed stillstand would be only the last phase of the ballistic motion which seems marked by a small bounce of the atmospheric layers on the photosphere. Then, a new shock wave, probably initiated by the iron κ-mechanism, sweeps the layers upward. There is some indications that the amplitude of the motion of atmospheric layers changes from one pulsation cycle to another one.