The temperatures, abundances and gravities of F dwarf stars.

Theoretical colours, computed using laboratory line data and model stellar atmospheres, have been used to interpret the colours of about 150 F and early G dwarfs. Effective temperatures have been derived from the Hfl index and from R-j, abundances have been obtained from mi and b-y and gravities have been obtained from Ci and b-y. The effective temperatures and gravities are in good agreement with values obtained from spectral scans. Much less observing time is required to obtain the colours than to obtain scans and the reduction procedure is also far simpler. Absolute magnitudes have been obtained from the effective temperatures and the gravities, the latter being used with assumed stellar masses to yield radii. The root mean square difference between photometric absolute magnitudes and trigonometric ones is about 0 4 magnitudes. The present results provide theoretical justification for the empirical formulae given by Crawford and by for the determination of absolute magnitudes and abundances from uvby photometry.