An unidentified absorption in the spectra of C-S stars

An absorption feature in the low-dispersion red spectrograms of carbon Mira variables and C-S stars shown to exhibit strikingly different behavior in these similarly appearing carbon and carbonlike stars. Evidence is presented that in the carbon Miras the feature may be due to unresolved bandheads of the (0,0) system of calcium iodide. In this group of stars the feature exhibits a temperature sensitivity similar to absorptions due to calcium chloride and to the neutral sodium doublet. No identification is suggested for the feature appearing among the C-S stars, though there is evidence against it being composed partially of a zero-volt line of neutral scandium.