CEPHEID VELOCITY CURVES FROM LINES OF DIFFERENT EXCITATION AND IONIZATION .1. OBSERVATIONS

Radial velocity curves have been obtained from several hundred optical absorption lines for FF Aql, delta Cep, eta Aql, and X Cyg. An iodine absorption cell has been used to reduce relative radial velocity errors to a few hundred meters per second. The shape and amplitude of the resulting radial velocity curves are in good agreement with previous results, particularly delta Cep which is shown to have been extremely constant over most of the last century. Velocities from atoms in low excitation potential (EP) levels (Fe I, Fe II, Sc II, Y II, Ti II) show positive velocity residuals of as much as 5 km s-1 compared to high EP Fe I lines during the phase of rapidly decreasing velocity. The 8.12 eV line of Si II at 6348 angstrom has a negative velocity residual during the same phase. The asymmetry of the high EP Fe I, Ti II, and the Si II lines are similar and greater than the asymmetry of the low EP Fe I, Fe II, Sc II, and Y II lines.