2006A&A...446..603S

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 (T_eff=3100K, logg=0.0 (cgs), ξ_t=2.2km/s) 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.