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Session 81 - Variable Cool and Late Type Stars.
Display session, Wednesday, January 15
Metropolitan Ballroom,

[81.05] The Physical Basis of MK Luminosity Classification in the A and F-type Stars

R. O. Gray, P. W. Graham, S. R. Hoyt (Appalachian State U.)

As part of a continuing project investigating the physical basis of luminosity classification in the late A, F and G-type stars, we report on the determination of the basic parameters (effective temperature, gravity, microturbulent velocity and metallicity), using classification-resolution spectra and spectral synthesis, of a number of A and F-type stars, ranging in luminosity class from dwarf (V) to supergiant (Ib). We confirm the suggestion made in earlier papers that microturbulence plays as large a role in the behavior of the MK luminosity criteria (based on lines of ionized species) as gravity, and discuss the existence of a correlation between gravity and the microturbulent velocity. The relevance of this study to the interpretation of MK spectral types is discussed as well.

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