The envelope of Pleione in 1976

In 1976 Pleione showed a further development of the shell characteristics. The spectrograms obtained in August and November 1976 were measured for the radial velocities, central intensities, and half half-widths of the shell lines of the Balmer series. The mean radial velocity was 8.7 kms-1 in August and 3.0 kms-1 in November. No Balmer progression was seen. The envelope continued its slow expansion in the equatorial plane as well as in the vertical direction. While the mean density in the envelope decreased due to expansion, the mass of the envelope increased up to 1.4 x 10-10 M sub(solar mass). The mass-loss rate was 4 x 10-11 M sub(solar mass)yr-1. The overall picture of the envelope is a smooth progression of the preceeding variation in 1972 - 1975. (author)