Evolution of the circumstellar disc of alpha Eri

Abstract

The Halpha line emission formation region in the circumstellar disc of alpha Eri is: a) extended with a steep outward matter density decline during low H$α$ emission phases; b) less extended with rather constant density distribution during the strong Halpha emission. The long-term variation of the Halpha emission has a 14-15 year cyclic B-Be phase transition. The disc formation time scales agree with the viscous decretion model. The time required for the disc dissipation is longer than expected from the viscous disc model.