R. Coronea Borealis vs Methane Spectrum

R. Core Borealis light curve from 1934 to 1940. The curve is immediately recognized as that of a gas due to the triplet of bands near 3.4 microns, termed P-Q-R. Gas specra are the only possessed of this feaure. A second set at longer wavelength is similar but lacking the Q branch. The nearest match is the IR spectrum of methane.