SIMBAD references

Using 288 high resolution spectra obtained over 3 consecutive years (1993-1995), the microturbulence velocity curve of δ Cephei is determined with a high temporal resolution. From the observed FWHM variation of the unblended FeI 5576.0883Å absorption line, and from nonlinear nonadiabatic pulsating models, it is shown that the global compression/expansion of the atmosphere provokes the variation of the turbulence. The turbulent velocity reaches its maximum, of about 7km/s, at minimum radius, and decreases up to 2km/s during the expansion of the star. It is also shown that the compression waves and shocks certainly provoke some rapid turbulence variations during their propagation in the atmosphere. The turbulence amplification due to these waves, being in general smaller than the global compression effect, increases with the wave amplitude.