This study of a well-observed Be star shows the enormous complexity of the variations observed. Several timescales were identified. There are periodic RV variations with a period of 1 372 and a variable amplitude. There are also long-term cyclic changes in the emission strength, and brightness and colours of the star. There are strong reasons to believe that the exact value of the 1 372 RV period varies. Most probably it undergoes a slow variation, possibly correlated with the long-term changes. The observed amplitude variation of the 1 372 RV curve can be formally described as the beating effect of two short periods, 1 372 and 1 35. Light variations prewhitened for the long-term changes and also the local mean RVs and locally derived RV amplitudes can be reconciled with a period of 34 675. There is also the possibility that even the value of the 1 372 period varies with this period.
One tentative interpretation considers a hierarchical system of three or even four stars. The long-term changes could be due to the most distant companion. It is noted that periods twice longer than the two short periods could be identified with the sidereal and synodic periods of a putative 34 675 binary system. The nature of the 1 372 RV variation is not clear and it is suggested that even this variation could be due to duplicity. At the moment, these suggestions are speculative, some even mutually exclusive. However, they can be tested and either confirmed or disproved by future well-planned observations.
© European Southern Observatory (ESO) 1998
Online publication: May 15, 1998