Presentation #208.04 in the session “Stars I”.
A subset of massive stars, called B-emission (Be) stars, are rapid rotators characterized by emission lines due to the presence of a gaseous circumstellar disk. We modelled the Be star Pleione (HD 23862) which has been observed to have variable emission lines that change from strong singly-peaked lines, to weak doubly-peaked lines and back to singly-peaked with a period of ~35 years. Different scenarios have been proposed to explain these changes. We developed a series of models to explain the observed variability associated with the Halpha emission line, infrared flux, and polarization in Pleione from 2005 to 2019, as it transitioned from a singly- to a doubly-peaked Halpha emission profile. We successfully reproduced the observed variability over time by establishing that the inclination of Pleione’s disk oscillates gradually between ~25⁰ and 90⁰ from the observed line-of-sight with an 82-year period.