Radiative energy flux changes of PLEIONE in the far-UV through the Be-shell ---> Be transition.
Mauron, N.; Doazan, V.; Barylak, M.; Cramer, N.; de La Fuente, A.
France, Spain, Switzerland
Abstract
We present far UV observations of Pleione made with the IUE satellite in the time-interval 1979-1991 which show, for the first time in the wavelength range 1250-3000 A, the dramatic changes of the FUV radiative energy flux between the Be-shell and the Be phases of a Be star. Between 1979, when Pleione exhibited a strong shell spectrum, and 1991, when it showed a Be-type spectrum, the observed far UV radiative energy flux increased by more than a factor two and the absorption bump at 2200 A showed large changes, clearly indicating that it cannot be used confidently for measuring the interstellar component of extinction in Be stars. Inspection of high resolution IUE spectra shows that at least part of these variations of the 2200 A bump is due to the variable contribution of a multitude of shell absorption lines which crowd the FUV spectrum.