The binary system 57 Cygni - apsidal motion and effects of spectral line blending.

Spectroscopic observations of 57 Cygni obtained at discrete intervals during the past 6o yr are discussed. An apsidal period of (203 + 4) yr is derived indicating a mean central condensation parameter k = ( j ). A study of a new series of spectrograms with fine-grained emulsion failed to reveal any of the weak absorption lines, arising from highly excited ions, which were detected and measured for radial velocity by Ovenden. Effects of blending of spectral lines on their measured positions are discussed and it is proposed that the radial-velocity anomalies determined by Ovenden are the consequence of this spectral line blending.