Variations of the amplitudes of oscillation of the Be star Achernar




We report on finding variations in amplitude of the two main oscillation frequencies found in the Be star Achernar, over a period of 5 yr. They were uncovered by analysing photometric data of the star from the Solar Mass Ejection Imager (SMEI) instrument. The two frequencies observed, 0.775 and 0.725 d−1, were analysed in detail and their amplitudes were found to increase and decrease significantly over the 5-yr period, with the amplitude of the 0.725 d−1 frequency changing by up to a factor of 8. The nature of this event has yet to be properly understood, but the possibility of it being due to the effects of a stellar outburst or a stellar cycle are discussed.