The gravity-darkening of the main-sequence components of spectral types A,F and G in detached close binary systems

From analysis of the photometric ellipticity effect in seven well-understood detached close binary systems, empirical values of the exponent α of gravity-darkening have been practically deduced for eleven main-sequence components of spectral types A, F and G which should cover the range of structural change (from radiative to convective) in stellar atmospheres. The result indicate that values of the exponent diminish gradually with decreasing effective temperatures from α ～ 1.0 for radiative atmospheres with T > 8500 K to α = 0.2 ～ 0.3 for convective atmospheres with T < 6500 K, in spite of some uncertainty in the reflection correction process.