Identification of FeH Lines in M, S and C Stars

Abstract

Using recent laboratory data of FeH molecular lines we attempt to identify the FeH absorption lines in the one-micron spectral region of late type stars, M dwarfs, M giants, S and C stars. The λ9910 absorption features in the spectrum of R Gem among the observed cool stars are identified as the FeH (0, 0) band lines. Results of our identifications are interpreted in view of the variation of C/O ratio in cool stars based on dissociation equilibrium theory. From our conclusion the appearances of absorption lines due to the metallic hydrides are discussed for cool stars.