A Binary Model for CH Cygni
Yasumasa Yamashita, Hideo Maehara · Publications of the Astronomical Society of Japan · 1979
Abstract Several spectrograms obtained at Okayama for CH Cygni during the period from 1967 to 1978 were measured for the radial velocity. From the velocity data compiled from the literature together with the present data, a probable period of about 5750 d was obtained for the orbital motion of the M-type star. The analysis of the velocity curve yields the following orbital elements: V0=—58.4 km s−1, K=6.8 km s−1, e=0.29, ω=201°, and T0=JD 2440023. A binary model is proposed in which the blue continuum comes from the hot gas around the companion, and emission lines of ionized metals are formed in a gaseous flow which streams from the M-type star to the companion. The Balmer emission lines originate in the circumstellar envelope around the companion. A great enhancement in the intensity of the circumstellar Balmer absorption observed in 1977 can be interpreted by this model.