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.