Flickering of the symbiotic variable CH Cygni during outburst.

Summary. High-speed and conventional BVRI photometry are reported for the bright symbiotic variable CH Cygni (M6 IlIe), obtained during the course of a recent outburst. Unlike the quiescent symbiotic stars, the presence of flickering similar in nature to that seen in the cataclysmic variables has been confirmed during this active phase. The BVRI photometry for a sample of stars in the field is used to derive the reddening (E (B- V) = 0.07) and the distance (r 600 pc) to CH Cyg. A composite energy distribution is derived from 0.35 to 11.0 ijm which clearly establishes the existence of a variable, blue continuum. The lack of variability in the near infrared (All AK AL < 0.10 mag) suggests that the blue continuum arises from a hot companion ((U-B) -1.1, (B-V) -0.3). A binary model including a subluminous hot companion accreting material from the stellar wind (M 1 /yr) of an SRa variable is discussed to account for the observed photometric properties.