A number of G and K-type giants show either strong or weak molecular
bands involving carbon. We illustrate two such stars here. HR 6791 is a G8
III (compare with the G8 III standard,
Gem) with a weak CN 4216
band, and
a very weak G-band (CH). Otherwise, the spectrum is fairly normal. HD
112127, a K2.5 III (compare with
Leo, K2 III), on the other
hand has an
exceptionally strong CN 4216 band, seen here as a pronounced depression in
the continuum shortwards of 4216 Å. In addition, it shows the 4737
Å C2
Swan band, and a clear depression of the continuum in the vicinity of 5200 ,
most probably due to the 5165 Å C2 Swan band. The
strength of these
molecular bands points to an abnormally high abundance of carbon in the
atmosphere of this star.
This figure uses 3.6 Å resolution flux spectra.
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