COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     Number 2398

                                    Konkoly Observatory
                                    Budapest
                                    7 September 1983

                                    HU ISSN 0374-0676




        THE RECENT SPECTROSCOPIC BEHAVIOUR OF CH CYGNI




  CH Cygni was known as a semiregular M6 III star until a blue continuum and
permitted and forbidden emission lines of metallic ions appeared for the
first time in 1963. Since then, there have been three separate periods of
activity in which this star showed a symbiotic spectrum. A program of 
spectroscopic observations of CH Cygni has been carried on for many years at the 
Observatory of Trieste, utilizing plates taken on purpose at the Observatoire
de Haute Provence. In particular, the entire period of activity begun in 1977
(and not yet ended) is covered by red and blue high dispersion spectra. Here
we give some preliminary results drawn from a visual-examination of the plates
from 1981 to August, 1983. Other publications are concerning the previous
years (Faraggiana and Hack, 1971, and Hack et al., 1982).

  During these two years the blue continuum was present with almost steady
strength, slightly tending to decrease. This can be argued from a slight 
increase of the absorption band strength, that we explain just in terms of a
reduced filling by the additional radiation. The Balmer lines maintained the
same appearence, both in the inverse P Cygni profiles and in the visibility
of the last terms. Halpha, Hbeta, Hgamma and Hdelta have two emission wings, with V>R.

  Between July and November, 1981, a lot of chromospheric absorption lines
became suddenly visible, and continued to deepen slowly as long as we have
observed the star. At the same time the forbidden lines lost much of their
intensity, and some of the [Fe II] lines disappeared in 1983, while the other
emission lines showed inverse P Cygni profiles. The resonance line of Ca I
at lambda 4227 had a central emission core in 1981; now a sharp absorption is 
visible in its place. Ionized calcium shows at least three narrow absorptions
in the H and K lines; before 1981 there were one or occasionally two wider
components, accompanied by a strong red emission.
  Coming to the longer wavelengths region, the situation is more stable: all
the lines of [O III] are always absent and those of O I (lambda6300, 
lambda6364) present an emission of constant intensity.

  This behaviour is not much different from that of the previous periods of
activity, except for the longer duration of this one and for the evident
appearance of inverse P Cygni-like profiles, that is now the principal trait
of the spectrum. Measurements of the radial velocities and of the line 
intensities are in progress.





              CONRAD BOEHM

              MARGHERITA HACK

              Observatorio Astronomico
              via G.B. Tiepolo 11
              casella postale
              succursale TS 5
              I-34131 TRIESTE Italy





References:

Faraggiana R. and Hack M. (1971): Astron. and Astroph. 15, 55 [BIBCODE 1971A&A....15...55F ]
Hack M., Rusconi, L., Sedmak, G., Engin, S. and Yilmaz, N. (1982): Astron. and
  Astroph. 113, 250 [BIBCODE 1982A&A...113..250H ]