Issue |
Astron. Astrophys. Suppl. Ser.
Volume 131, Number 2, August 1998
|
|
---|---|---|
Page(s) | 229 - 237 | |
DOI | https://doi.org/10.1051/aas:1998265 | |
Published online | 15 August 1998 |
CH Cygni 1987-89: The inactive state as a precursor to the new outburst
Faculty of Education, Omladinska 14, HR-51000 Rijeka, Croatia
Received:
22
August
1997
Accepted:
4
February
1998
In order to help answering the question generally posed for symbiotic stars: are the
apparently inactive periods quiescent at all, or should they be regarded merely
as a transition between adjacent outbursts, we tried to establish correlation between the
subtle phenomena in the time evolution of the cool giant's photosphere and emission line
profiles of the symbiotic star CH Cygni during the period 1987-89. Optical spectra of
this star in its inactive state taken at the Haute Provence Observatory as well as the spectra
of late type giant's of the same spectral type have been used. The comparison of the
results obtained suggests that the time evolution of the physical parameters of CH Cyg
reflect the symbiotic phenomena rather than the intrinsic variability of the cool
component. The time behaviour of the Balmer emission line profiles rules out the general
validity of the established models. An acceptable model valid at least for the observed
period has been proposed. According to it, an envelope of variable optical thickness
surrounds the hot component. The development
of its inner radius, of and
line profiles and of the
nebular line leads to the conclusion that the inactive state is not stationary, but is gradually evolving in time toward the new activity of the
star.
Key words: stars: binaries: symbiotic / stars: CH Cygni
© European Southern Observatory (ESO), 1998