A high-resolution spectroscopic analysis of the supergiant HD 165553

The results of an analysis of a high-resolution spectrum of the possible spectroscopic binary HD 165553, obtained with a spectral resolving power of similar to 60 000, are presented. A detailed chemical-composition study indicates that the star is a normal supergiant with essentially solar composition except for the elements C and Na, for which we present plausible reasons associated with stellar evolution. Comparison of the star's spectrum with that of gamma Cyg, a supergiant of spectral type F8 lab, indicates that the star is of a later spectral type; we assign a spectral type Go lab for the star. The star may be a single-lined spectroscopic binary; there is no evidence of double lines in its spectrum. The heliocentric radial velocity of the star is estimated on our spectrum to be - 4.5 km s(-1) +/- 1.5 km s(-1).