The varying spectrum of the Mira type star S Carinae

Top: optical and near-IR spectrum in normalized units of energy per unit wavelength. The wavelengths in nanometers are given above the plot. Bottom: Simplified light curve: the visual magnitude is plotted versus time in months.
S Carinae is a relatively warm pulsating variable of the type of Mira.

This animation (which clearly isn't perfect...) was produced using 4 spectra taken along one pulsation cycle (see Lançon and Wood 2000).

The light curve of S Carinae is not quite as regular as illustrated in the bottom graph, but has about that optical amplitude.

The animated spectra are normalized to a constant bolometric luminosity. In reality, the near-IR light varies in phase with the optical light. However, due to the large change in effective temperature along the cycle, the near-IR amplitude is much smaller than the optical amplitude.

Note the hydrogen emission lines near maximum light, and the deep molecular bands (TiO, VO, H2O) around minimum light.