The activity phase of CH Cygni during the period 1967 to 1970.
Abstract
The spectrum of CH Cygni during the period July 1967-December 1970, following the explosion of June 1967, has been studied using high dispersion spectrograms. The main characteristics are the following: a) The M6 spectrum is veiled by a continuum which partially fllls the absorption lines and increases in intensity toward the violet. This continuum was absent in August 1965 and in September 1970; it appeared at the moment of the explosion, in June 1967, as observed by Deutsch, and reached a maximum in August 1968. The color temperature was about 10000 0K. No measurable Balmer discontinuity was observable. b) Emission lines of He r, Fe tr, [Fe fl] and [S fl], are present. The Balmer lines and the H and K lines present a P Cygni contour. The Balmer decrement is close to the decrement observed for the Be stars. Th July and August 1968 H and K presented two sharp absorption cores at B V of about -75 km/s and -160 km/s. In July 1968 the nebular line 5007 [0 in] appeared. The ensissions reached maximum intensity in August 1968 and in August 1969. In August 1965 and in September-December 1970 the spectrum was a normal M6 Ill type, except that Hcc and HO presented emission components. c) Absorption chromospheric lines, which were completely missing in July 1967, appeared in the ultraviolet continuum in July 1968. Ouly lines of metallic ions were present. Th May 1970 the ultraviolet lines of high excitation, like those of Cr TI, had disappeared, and several lines of neutral metaffic atoms appeared. At this epoch the lines of low excitation at < 3800 give radial velocities systematically more negative by about -20 km/s than the other lines having the same low level. The strong resonance lines behave like the ultraviolet lines. The radial velocities give evidence of stratffication effects. Several levels -photosphere, low liromosphere, high chromosphere, outer be distinguished. A curve of growth constructed with the chromospheric absorption lines gives an excitation temperature of about 5000 0K in August 1968 and 3600 0K in May 1970. The microturbulence ranges from 15 km/s in 1968 to 9 (Ti II) and 4 (Co I, Ni I) in 1970. The various hypotheses proposed for explaining the symbiotic stars are examined. No clear evidence in favor of the presence of a hot companion is given by our observations. Key words: CH Cygni - symbiotic - radial velocity - spectral variations
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 1971
- Bibcode:
- 1971A&A....15...55F