engleski

Atmospheric thermal structure of a sample of M type giants

The evolution of binary systems depends strongly on the mass transfer beetwen the two components, the one of which is often a late type giant. In order to understand it and in the case when the mass transfer occurs via stellar wind, it is important to investigate the thermal structure of the giant's photosphere. The calibration of effective temperature scale and establishment of its correlation to the excitation temperature for different spectral subtypes has significant implications in determination of the atmospheric structure for cool giant stars. We took the sample of 10 M type giants of luminostiy class III and subtypes M2-M8 located in the Galactic plane and determined their vibrational temperatures from the gamma band system of the TiO molecule. The relationship between Texc and Teff has proved to be sensitive to the choice of the Teff calibration scale. The deviations of Texc with respect to the Teff for our stars have been used as an indicator of the depth of the atmospheric layers in which molecular bands are formed.

M giant stars; stellar atmospheres

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