The period of maximum brightness of CH Cygni which started in mid 1981 finished at the end of July 1984, when sudden drop by about 1 mag was observed (Fig.1). At the same time a radio outburst has occured and the jet structure has developed (Taylor et al.1986). The Toruń Observatory has recorded the spectra of CH Cygni just at this moment. Significant spectral variations, especially development of wide wings in Balmer emission lines have been found (Mikołajewski and Tomov 1985).
Mikołajewski et al. (1987) showed that the “shell” absorption lines roughly reflect the orbital motion of a hot companion of the M giant. Figure 1 presents radial velocities of these absorption lines of ionized and neutral metals (mainly TiII, FeI) together with the v.rad. followed from possible orbital solution suggested by Mikołajewski et al. About 3-4 days after the drop started the RVs of the “shell” absorption lines very quickly (during 3 days) got out of a deep local minimum (ΔV ∼15–20 km/s) preceding the drop by a mounth. The FeII emission lines, which are formed in the outer regions, do not show so large radial velocity variations ( Fig.1 ).