Volume 446, Number 2, February I 2006
|Page(s)||603 - 609|
|Section||Stellar structure and evolution|
|Published online||13 January 2006|
An abundance analysis of the symbiotic star CH Cygni
N. Copernicus Astronomical Center, ul. Rabiańska 8, 87-100 Toruń, Poland e-mail: firstname.lastname@example.org
2 Institute of Atomic Physics and Spectroscopy, University of Latvia, Raiņa bulvāris 19, 1586 Rīga, Latvia e-mail: email@example.com
3 N. Copernicus Astronomical Center, ul. Bartycka 18, 00716 Warsaw, Poland e-mail: firstname.lastname@example.org
4 National Optical Astronomy Observatory, PO Box 26732, Tucson, AZ 85726, USA e-mail: email@example.com
Accepted: 12 September 2005
The photospheric abundances for the cool component of the symbiotic star were calculated for the first time using high-resolution near-infrared spectra and the method of of standard LTE analysis and atmospheric models. The iron abundance for CH Cyg was found to be solar, [Fe/H] = 0.0 ± 0.19. The atmospheric parameters (Teff = 3100 K, (cgs), km s-1) and metallicity for CH Cyg are found to be approximately equal to those for nearby field M7 giants. The calculated [C/H] = -0.15, [N/H] = +0.16, [O/H] = -0.07, and the isotopic ratios of 12C/13C and 16O/17O are close to the mean values for single M giants that have experienced the first dredge-up. A reasonable explanation for the absence of barium star-like chemical peculiarities seems to be the high metallicity of CH Cyg. The emission line technique was explored for estimating CNO ratios in the wind of the giant.
Key words: binaries: symbiotic / stars: abundances / stars: late-type / stars: individual: CH Cyg
© ESO, 2006
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