THE FUNDAMENTAL PARAMETERS OF FIELD HORIZONTAL-BRANCH STARS

The fundamental parameters (T-eff, log(g), and [M/H]) for a set of 56 field horizontal-branch candidates have been determined using Stromgre n uvby photometry, classification-dispersion CCD spectra and spectral synthesis. In the T-eff, log(g) plane, the majority of these stars lie near to the model zero-age horizontal branches of Sweigart (1987) and thus are probable field horizontal-branch stars. Four are normal high -gravity dwarfs which may be field counterparts of cluster blue stragg lers and one may belong to the class of ''UV-bright'' stars. One new, probable, RR Lyrae star has been identified. We discuss two FHB stars which cannot be modeled with normal helium-abundance atmospheres. We s uggest that these two stars, which have Palmer lines too broad for the ir Balmer jumps, may be helium-rich horizontal-branch stars. Finally, we discuss the problems of the discrimination of FHB stars from ''norm al'' evolved A-type stars, and the nature of the FHB ''lambda-Bootis-l ike'' stars discovered in Paper I of this series. (C) 1996 American As tronomical Society.