Infrared analysis of a Mira-type variable, Omicron Ceti



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The physical properties of a class of late spectral type giant stars, called Mira-type variables, and the use of infrared Fourier spectroscopy in their analysis are reviewed in this paper. The one micron and two micron regions of the infrared spectrum of Omicron Ceti (o Get) , the prototype of this class of stars, is examined for spectral classification and for the determination of the principle molecular constituents in a Mira-type stellar atmosphere. As a result, an effective temperature, T[lowered e] = 1960 ± 100°K corresponding to a spectral classification of M 8.0e and a phase 0.48 was derived. Oxide bands of titanium and vanadium in the one micron region and of carbon and silicon in the two micron region were found. An estimate of the stellar water vapor content based on an examination of the visible portion of the spectrum yields a value of 5.0 X 10[raised 21] molecules/cm[raised 2] for o Get at this temperature and phase. A comparison of the present results to those expected for an M 8 giant atmosphere agree with Spinrad and Vardya's (1966) suggestion that an oxygen to carbon ratio close to unity for Mira-type stellar atmospheres is preferred.