Dramatic Spectral and Photometric Changes of Pleione (28 Tau) between 2005 November and 2007 April

Abstract

Abstract Recent photometric and spectroscopic observations of Pleione are reported. Pleione showed brightness declines in both the $B$ and $V$ bands by $\sim$ 0$\rlap {.}{^{\rm m}}$25 between 2006 January and 2007 March. Significant decreases in the strengths and widths of the long-lived emission components in H$\alpha$ and H$\beta$ were observed during this period, while additional outer double-emission components appeared in these lines. Many metallic shell lines strengthened during the observation period, being accompanied by central quasi-emission components. We interpret these spectral changes in terms of a double disk: the progressive decline of a misaligned old disk in due course of precession and the formation and growth of a new disk in the star’s equatorial plane.