Cyclic variability of the circumstellar disk of the Be star zetaTau - I. Long-term monitoring observations
Cyclic variability of the circumstellar disk of the Be star zetaTau - I. Long-term monitoring observations
Emission lines formed in decretion disks of Be stars often undergo long-term cyclic variations, especially in the violet-to-red (V/R) ratio of their primary components. From observations of the bright Be-shell star zeta Tau, the possibly broadest and longest data set illustrating the prototype of this behaviour was compiled from our …