Chemical analysis of the selected galactic red giant stars

In this thesis, surface chemical abundances of some selected red giant members of the NGC 752, NGC 6940 and Hyades open clusters were analyzed by using the high resolution (R ≈ 60 000) and high signal to noise ratio (S/N ≥ 120) spectra. Cluster memberhips were confirmed by measuring the stellar radial velocities. By applying isochrones to the colour-magnitude diagrams, age and turn-off mass parameters of the clusters were determined. Model atmosphere parameters (Teff, log g, [Fe/H] and ξt) were found via equivalent widths of the Fe I, Fe II, Ti I, and Ti II lines. Metallicities of the open clusters NGC 752, NGC 6940 and Hyades were derived as [Fe/H]= −0.02 ± 0.05, [Fe/H] = 0.04 ± 0.02 ve [Fe/H] = 0.12 ± 0.04, respectively. Abundances of the light odd-Z (Na, Al), α (Mg, Si, Ca), Fe-group (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn), and n-capture (Y, La, Nd, Eu) elements were calculated by using the equivalent width or synthetic spectrum analysis methods. The abundances of LiCNO and 12C/13C ratio were also determined. Lithium abundances were derived from the Li I 6707 Å resonance doublet and oxygen abundances were analyzed from the forbidden [O I] line at 6300 Å. Carbon abundances were determined using the CH G-band feature located near 4300 Å and the C2 Swan bandheads at 5165 and 5635 Å. Nitrogen abundances and 12C/13C were derived from 12,13CN molecular bands in the 7995-8040 Å region. By using the LiCNO abundances and, 12C/13C ratios along with the photometric data, evolutionary status of the red giants was estimated and the results were discussed in terms of stellar evolution theories.