Spectrophotometry of the continuous spectrum of pleione during 1972-1986

Many years of observations of Pleione (during 1972-1986) with low-resolution spectrometers have yielded energy distributions in the continuum and equivalent widths of the lines Hα - Hδ. It is noted that there is a correlated (but shifted in time) variation of the brightness in V and equivalent width of the emission line Hα. The variations of the Balmer jump and of the ultraviolet gradient are well correlated with the variations of the color index U-B. Comparison of the observed continuum with the energy distribution in stars according to Kurucz's models and the energy distribution of a hydrogen gas has shown that the contribution of the gas component, transparent in the continuum, to the total radiation decreased from ∼ 2.7% in 1970 to ∼ 0.8% in 1975. The strong development of the absorption line spectrum formed in the circumstellar envelope during 1977-1985 helped to block the stellar radiation beyond the Balmer jump and lower the spectrophotometric temperature in this spectral region. The color and spectral properties of the star in 1986 matched its radiation for Teff = 11,500 degree K, this indicating significant dispersion of the envelope. The emission measure of the envelope in 1975 was ∼ 1.6 x 1035 cm-5 and its mass ∼ 5 x 10-10 MassSun. 33 refs., 4 figs