The vanishing shell phase of PLEIONE in the far UV in 1988.

Far UV observations made with the IUE in 1988, when the shell spectrum of Pleione was vanishing in the visible region, are compared with previous IUE observations made when the shell was strong (1979) and when it began to weaken (1985). Between the epochs of strong shell and vanishing shell: (1) the apparent continuum level increases in all the observed far UV spectral range, the largest increase occurring at shortest wavelengths; (2) the CIV and SiIV resonance lines, which were not detectable during the epoch of strong shell, are identified without ambiguity in this B8Ve star when the shell spectrum vanishes; and (3) when the shell spectrum is strong, the MgII resonance lines exhibit a strong, broad absorption. When the shell spectrum vanishes, this absorption is much weaker and the MgII doublet shows double emission peaks with deep absorption cores, as is often observed in Be/shell spectra.