SIMBAD references

We present spectroscopic data covering 1978-1994 and photometric data covering 1984-1992 of ζ Tau obtained at the Xinglong Station of Beijing Astronomical Observatory. The photometric observations are made in the standard UBV system. To study the spectroscopic behaviour in detail, we measured the radial velocities of the shell absorption lines and the V/R ratio, the equivalent width, and the peak separation of the Hα emission line. The results show that: 1) the mean radial velocity of Balmer lines (Hγ, Hδ and Hε) exhibited cyclic variations in 1978-1985. The first cycle ceased around 1982, but the second was shorter and the amplitude was smaller. During 1986-1990, the velocity values diminished conspicuously and the cyclic variation also disappeared; 2) the variations of the V/R ratio of Hα were in phase with the radial velocity curve before 1982. The V/R ratios fluctuated in an irregular manner during 1983-1988. The cyclic changes of the V/R ratio reappeared after 1988; 3) the equivalent width of the Hα emission decreased gradually from 29A in 1978-1979 to 6A in 1988 and then increased to 24A in 1992; 4) the variations of the peakseparation of Hα were small in 1978-1982 and after 1990, but its amplitude became evidently larger during 1983-1989; 5) the star showed evident variations in U, B and V which were correlated to V/R variations of Hα in 1990-1992. In addition to the long-term variations on a time scale of years, we also observed some night-to-night activities and even more rapid changes, but they usually occurred at the beginning or the end of cyclic variations. In addition, we have made preliminary estimates of the physical character and dimensions of the emission envelope of the star in different observation periods. Finally, three structural modellings are summarized to explain the V/R cyclic variations. We have attempted to compare the variations observed with those predicted, proposing more convincing interpretations.