SIMBAD references

The monitoring of the H-alpha emission profile of zeta Tau for more than 5 years (JD 2455500 to JD 2457500) enables the study of the time behavior of the central absorption core (CA) of that profile. During this time section the circumstellar disk of zeta Tau had a minimum of mass. On the base of 145 high resolved spectra of the ARAS-spectroscopy group the strength of the CA minima has been evaluated. The period analysis of that time series data led to a period of 442 days. That period has been attributed to the nodding period and hence to the precession period of zeta Tau's disk during the time section mentioned above.