SX Cen

A galactic RV Tauri type star. SX Cen is an example of the spectroscopic "B" (carbon-rich) group of the RV Tauri stars, which are characterized by Ca II lines that are too weak for the spectral type suggested by the H lines and by very strong CN absorption at 3883 Å when near minimum light. CH is also enhanced near minimum, while both CH and CN are absent at maximum light. SX Cen shows these features to a particularly marked degree, it shows weak C2 bands at 5165 and 4737 Å. Similarly weak bands of C2 have been seen in AC Her and in GK Car.