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Paper: Spectral and Photometric Evolution of V725 Tau (1996-1999): Towards a Shell Phase?
Volume: 214, The Be Phenomenon in Early-Type Stars, IAU Colloquium 175
Page: 569
Authors: Piccioni, A.; Bartolini, C.; Bernabei, S.; Galleti, S.; Giovannelli, F.; Guarnieri, A.; Sabau-Graziati, L.; Valentini, G.; Villada, M.
Abstract: HDE 245770=V725 Tau, the optical counterpart of A0535+26, presented in the last three years a period of uncommon optical faintness and of exceptionally low spectral activity. Photometric data obtained in 1997 and 1998 show a fading in all color, followed in 1999 by a nearly costant phase in which the star attained the lowest level of the last 23 years. In 1998 the emission lines became much fainter than in 1997, changing slowly from emission to absorption. In November 1998 only H alfa was still showing a weak emission with an absorption core; this behaviour suggest the occurrence of a shell phase.
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