Basic parameters for 372 A, F & G stars

In this paper, a multidimensional downhill simplex technique is introduced to determine the basic parameters of the program stars from fits of synthetic spectra and fluxes with observed spectra and fluxes from Strvmgren uvby photometry.

This exercise yields useful calibrations of the MK spectral classification system but, most importantly, gives insight into the physical nature of luminosity classification on the MK spectral classification system. In particular, we find that in this range of spectral types, microturbulence appears to be at least as important as gravity in determining the MK luminosity type.