The spectrum variations of PLEIONE from 1938 to 1975

Spectrophotometric data on the shell episode of Pleione from 1938 to 1954 have been amassed. Changes in the emission profiles, absorption-line intensities and asymmetries, and the Balmer progression are studied. The latter is shown to be related to differential asymmetries along the Balmer series. A very broad component of the Ca II K line is found to be closely related to the mass-loss rate and to be a precursor of new shell activity. The emission phase of Pleione from 1969 to 1971 and the new shell phase from 1972 to 1975 are also examined. The radial velocities of the shell and star are shown to be equal and to have no significant variations. Good agreement is found between the stellar-wind model and the observed variations, with the exception of the emission intensity and the Balmer progression.