The average physical properties of A-G stars derived from uvby-H β Strömgren-Crawford photometry as the basis for a spectral-classification synthetical approach

We have revisited and updated the uvby Strömgren colour and colour-index distributions of A-, F-, and early G-type main-sequence stars. For this aim, we selected 7054 dwarf stars along with 65 Morgan-Keeman (MK) standard stars within the same spectral range but covering all luminosity classes. The standard stars were selected following the MK mandate strictly, using spectra taken at classification resolution recorded on photographic plates. We used the colours of these stars to determine the effective temperature and surface gravity. After correcting for systematic offsets using fundamental parameters and considering a few exceptions, we find a one-to-one correspondence, among MK spectral types, Strömgren photometry, and their associated physical properties.