Halpha profiles for G-type dwarfs and subgiants.

Summary. The Hoc wing profiles have been computed from model atmospheres for G-type dwarfs and subgiants of various compositions. The profiles are insensitive to gravity and to helium abundance, but quite sensitive to metal abundance in addition to effective temperature. The metal abundance variation is in the sense that metal-poor stars have stronger Hoc lines than normal composition stars of the same temperature. However, a study of the observed profiles in eighteen stars whose metal abundances are also measured, shows that the observed sensitivity of the Hoc wings to metal abundance is somewhat greater than that predicted by the models. Key words: Hoc profiles - G-dwarfs subgiants - abundance variations