This argument is only strictly valid if we assume that the B[e] phenomenon is a special phase (for stars with perhaps very specific initial conditions) during single star evolution, which we will assume throughout this paper. If the B[e] phenomenon for these supergiants is caused by some binary interaction or binary merger process, the situation might be completely different.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

Note that by writing CO without indication of the isotope, we always refer to the main isotope, i.e., the ¹²CO molecule.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

... edges

For clarification, we use the terminus band head when talking about the intensity peaks, while the transition of lowest wavelength in each band we call the band edge.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.