2001A&A...378..455K

CCD spectra obtained with the echelle spectrometer of the 6-meter telescope were used to determine, by the model atmospheres method, the fundamental parameters (T_eff=4800K, logg=0.7) and detailed chemical abundances for the star K413, a member of the globular cluster M12. The resulting value, [Fe/H]=-1.38, is the first metallicity determination for M12 using high-resolution spectra. The main characteristic feature of the star's atmospheric chemical abundance pattern is a large oxygen excess, [O/Fe]≃+2. The s-process elements are probably slightly depleted compared to metallicity: [X/Fe]=-0.04 for yttrium and zirconium, [Ba/Fe]=-0.12 for barium. Abundances of the heavier elements: La, Ce, Nd, and Pr, do not differ, relative to iron, from the solar ones: [heavy/Fe]=0.0. The europium excess, [Eu/Fe]=+0.48, is typical of members of low-metallicity globular clusters. The spectrum of K413 shows, for the Hα line, an variable absorption and emission profile. From its high luminosity and chemical abundance anomalies, we can suppose that K413 is in an evolutionary stage after the AGB. In the spectrum, we find absorption details that can be identified with diffuse interstellar bands displaced by 16km/s to longer wavelengths relative to the star's velocity.