Atmospheric and photospheric variations of δ Cep are plotted against its pulsation phase. The top two panels show FUV emission line variations with phase, and the third panel shows variations of the star’s X-ray flux. Pink data points in the third panel represent measures made by XMM-Newton, and cyan data points show the follow-up observations made in 2015 with Chandra. For reference, the fourth and fifth panels show the V-band light curve and radial curve, respectively (RV curve from Kiss 1998). The bottom panel shows the variations of the star’s angular diameter with the pulsation phase from Mérand et al. (2015).