Spectrum Variations in A-Type Supergiants

A detailed investigation has been made of the changes in line strengths and microturbulence in the three high4uminosity A stars 6 Cas (A3 Ia+), 9 Per (A2 Ia), and Cep (A2 Ia). The results of the analysis suggest the existence of a correlation among absolute magnitude, mean value of the microturbulence, and amplitude of variability of both microturbulence and radial velocity. In addition, the presence of a strong correlation between the behavior of the micro turbulence and the radial velocity in the case of 6 Cas and 9 Per indicates the existence of a strong coupling between large-scale and small-scale mass motions in the high4uminosity A stars and provides observational evidence for the occurrence of nonlinear aerodynamic processes in the atmospheres of these stars.