TIME-RESOLVED HIGH-RESOLUTION SPECTROSCOPY OF CH-CYGNI - EVIDENCE FORA MAGNETIC PROPELLER STATE IN 1994

We present high-resolution, time- and spatially resolved spectroscopic observations of CH Cyg carried out in the period 1994 May-August. A t ime resolution of similar to 10 min and S/N ratios up to 300 have been achieved. Large variations in the main peak as well as in the wings o f hydrogen emission lines have been observed to evolve on time-scales from minutes to days. Discrete emission components on the red and blue sides of the main emission peak reach velocities in excess of 2000 km s(-1). Blueshifted absorption components cluster at mean velocities - 500 km s(-1) and -700 km s(-1). The presence of these high-velocity, h ighly variable components is explained in terms of a magnetic propelle r state of the star on its way toward a new bright maximum. A low-dens ity nebula at l-arcsec distance from CH Cyg and aligned with the direc tion of the 1984 radio jet is seen in [N II], and tentatively confirme d in [O III].